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Pan MK. Targeting the fundamentals for tremors: the frequency and amplitude coding in essential tremor. J Biomed Sci 2025; 32:18. [PMID: 39924504 PMCID: PMC11809078 DOI: 10.1186/s12929-024-01112-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2024] [Accepted: 12/12/2024] [Indexed: 02/11/2025] Open
Abstract
Essential tremor (ET) is one of the most common movement disorders with heterogeneous pathogenesis involving both genetic and environmental factors, which often results in variable therapeutic outcomes. Despite the diverse etiology, ET is defined by a core symptom of action tremor, an involuntary rhythmic movement that can be mathematically characterized by two parameters: tremor frequency and tremor amplitude. Recent advances in neural dynamics and clinical electrophysiology have provided valuable insights to explain how tremor frequency and amplitude are generated within the central nervous system. This review summarizes both animal and clinical evidence, encompassing the kinematic features of tremors, circuitry dynamics, and the neuronal coding mechanisms for the two parameters. Neural population coding within the olivocerebellum is implicated in determining tremor frequency, while the cerebellar circuitry synchrony and cerebellar-thalamo-cortical interactions play key roles in regulating tremor amplitude. Novel therapeutic strategies aimed at tuning tremor frequency and amplitude are also discussed. These neural dynamic approaches target the conserved mechanisms across ET patients with varying etiologies, offering the potential to develop universally effective therapies for ET.
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Affiliation(s)
- Ming-Kai Pan
- Department and Graduate Institute of Pharmacology, National Taiwan University College of Medicine, No. 1, Sec. 1, Ren-Ai Road, Taipei, 100, Taiwan.
- Molecular Imaging Center, National Taiwan University, Taipei, Taiwan.
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
- Cerebellar Research Center, National Taiwan University Hospital, Yun-Lin Branch, Yun-Lin, Taiwan.
- Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan.
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2
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Chang I, Chung T, Kim S. Wavenumber-dependent transmission of subthreshold waves on electrical synapses network model of Caenorhabditis elegans. eLife 2025; 13:RP99904. [PMID: 39773527 PMCID: PMC11709431 DOI: 10.7554/elife.99904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2025] Open
Abstract
Recent experimental studies showed that electrically coupled neural networks like in mammalian inferior olive nucleus generate synchronized rhythmic activity by the subthreshold sinusoidal-like oscillations of the membrane voltage. Understanding the basic mechanism and its implication of such phenomena in the nervous system bears fundamental importance and requires preemptively the connectome information of a given nervous system. Inspired by these necessities of developing a theoretical and computational model to this end and, however, in the absence of connectome information for the inferior olive nucleus, here we investigated interference phenomena of the subthreshold oscillations in the reference system Caenorhabditis elegans for which the structural anatomical connectome was completely known recently. We evaluated how strongly the sinusoidal wave was transmitted between arbitrary two cells in the model network. The region of cell-pairs that are good at transmitting waves changed according to the wavenumber of the wave, for which we named a wavenumber-dependent transmission map. Also, we unraveled that (1) the transmission of all cell-pairs disappeared beyond a threshold wavenumber, (2) long distance and regular patterned transmission existed in the body-wall muscles part of the model network, and (3) major hub cell-pairs of the transmission were identified for many wavenumber conditions. A theoretical and computational model presented in this study provided fundamental insight for understanding how the multi-path constructive/destructive interference of the subthreshold oscillations propagating on electrically coupled neural networks could generate wavenumber-dependent synchronized rhythmic activity.
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Affiliation(s)
- Iksoo Chang
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and TechnologyDaeguRepublic of Korea
- Creative Research Initiative Center for Proteome Biophysics, Daegu Gyeongbuk Institute of Science and TechnologyDaeguRepublic of Korea
- Supercomputing Bigdata Center, Daegu Gyeongbuk Institute of Science and TechnologyDaeguRepublic of Korea
| | - Taegon Chung
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and TechnologyDaeguRepublic of Korea
| | - Sangyeol Kim
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and TechnologyDaeguRepublic of Korea
- Creative Research Initiative Center for Proteome Biophysics, Daegu Gyeongbuk Institute of Science and TechnologyDaeguRepublic of Korea
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3
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Sultan ZW, Najac M, Raman IM. Control of action potential afterdepolarizations in the inferior olive by inactivating A-type currents through K V4 channels. J Physiol 2024. [PMID: 39303148 PMCID: PMC11922792 DOI: 10.1113/jp286818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Accepted: 08/07/2024] [Indexed: 09/22/2024] Open
Abstract
Neurons of the inferior olive (IO) fire action potentials with large, long-lasting afterdepolarizations (ADPs). Broader ADPs support more spikes in climbing fibre axons and evoke longer bursts of complex spikes in Purkinje cells, which affect the magnitude and sign of cerebellar synaptic plasticity. In the present study, we investigated the ionic mechanisms that regulate IO action potential waveforms by making whole-cell recordings in brainstem slices from C57BL6/J mice. IO spikes evoked from rest had ADPs of ∼30 ms. After 500-ms hyperpolarizations, however, evoked action potentials were brief (1-2 ms), lacking ADPs altogether. Because such preconditioning should maximally recruit depolarizing Ih and T-type currents and minimize repolarizing Ca-dependent currents known to shape the ADP, the rapid action potential downstroke suggested additional, dominant recovery of voltage-gated K currents at negative voltages. Under voltage clamp, outward currents evoked from -98 mV included large, voltage-gated, rapidly inactivating 'A-type' K currents. These currents had a steep availability curve with half-inactivation at -85 mV, suitable for recruitment by small hyperpolarizations. The fast decay time constant increased with depolarization, as is typical of KV4 channels. The KV4 channel blocker AmmTx3 almost eliminated inactivating currents and broadened action potentials evoked from strongly negative potentials by ∼8-fold. Optogenetic stimulation of inhibitory cerebellar nucleo-olivary terminals hyperpolarized IO cells sufficiently to abolish the ADP. The data support the idea that currents through KV4 channels control action potential waveforms in IO cells, shortening ADPs during synaptic inhibition or troughs of membrane potential oscillations, thereby controlling the number of climbing fibre action potentials that propagate to the cerebellum. KEY POINTS: Neurons in the mouse inferior olive (IO) express a large, inactivating, voltage-gated A-type K current carried by KV4 channels. IO action potentials evoked from rest have large, long afterdepolarizations that disappear with pre-spike hyperpolarizations of 5-15 mV. The steep voltage-sensitivity and rapid recovery of KV4 channels regulates the duration of the afterdepolarization over more than one order of magnitude. Factors such as synaptic inhibition are sufficient to recruit KV4 channels and eliminate afterdepolarization (ADP). By controlling the ADP, KV4 channels can set the number of climbing fibre action potentials relayed to the cerebellum and regulate plasticity implicated in motor learning.
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Affiliation(s)
- Ziyad W Sultan
- Department of Neurobiology, Northwestern University, Evanston, IL, USA
- Northwestern University Interdepartmental Neuroscience Program, Northwestern University, Evanston, IL, USA
| | - Marion Najac
- Department of Neurobiology, Northwestern University, Evanston, IL, USA
| | - Indira M Raman
- Department of Neurobiology, Northwestern University, Evanston, IL, USA
- Northwestern University Interdepartmental Neuroscience Program, Northwestern University, Evanston, IL, USA
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Miles KD, Barker CM, Russell KP, Appel BH, Doll CA. Electrical Synapses Mediate Embryonic Hyperactivity in a Zebrafish Model of Fragile X Syndrome. J Neurosci 2024; 44:e2275232024. [PMID: 38969506 PMCID: PMC11293453 DOI: 10.1523/jneurosci.2275-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 06/19/2024] [Accepted: 06/27/2024] [Indexed: 07/07/2024] Open
Abstract
Although hyperactivity is associated with a wide variety of neurodevelopmental disorders, the early embryonic origins of locomotion have hindered investigation of pathogenesis of these debilitating behaviors. The earliest motor output in vertebrate animals is generated by clusters of early-born motor neurons (MNs) that occupy distinct regions of the spinal cord, innervating stereotyped muscle groups. Gap junction electrical synapses drive early spontaneous behavior in zebrafish, prior to the emergence of chemical neurotransmitter networks. We use a genetic model of hyperactivity to gain critical insight into the consequences of errors in motor circuit formation and function, finding that Fragile X syndrome model mutant zebrafish are hyperexcitable from the earliest phases of spontaneous behavior, show altered sensitivity to blockade of electrical gap junctions, and have increased expression of the gap junction protein Connexin 34/35. We further show that this hyperexcitable behavior can be rescued by pharmacological inhibition of electrical synapses. We also use functional imaging to examine MN and interneuron (IN) activity in early embryogenesis, finding genetic disruption of electrical gap junctions uncouples activity between mnx1 + MNs and INs. Taken together, our work highlights the importance of electrical synapses in motor development and suggests that the origins of hyperactivity in neurodevelopmental disorders may be established during the initial formation of locomotive circuits.
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Affiliation(s)
- Kaleb D Miles
- Section of Developmental Biology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Chase M Barker
- Section of Developmental Biology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Kristen P Russell
- Section of Developmental Biology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Bruce H Appel
- Section of Developmental Biology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Caleb A Doll
- Section of Developmental Biology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
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Nakayama A, Watanabe M, Yamashiro R, Kuroyanagi H, Matsuyama HJ, Oshima A, Mori I, Nakano S. A hyperpolarizing neuron recruits undocked innexin hemichannels to transmit neural information in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2024; 121:e2406565121. [PMID: 38753507 PMCID: PMC11127054 DOI: 10.1073/pnas.2406565121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Accepted: 04/19/2024] [Indexed: 05/18/2024] Open
Abstract
While depolarization of the neuronal membrane is known to evoke the neurotransmitter release from synaptic vesicles, hyperpolarization is regarded as a resting state of chemical neurotransmission. Here, we report that hyperpolarizing neurons can actively signal neural information by employing undocked hemichannels. We show that UNC-7, a member of the innexin family in Caenorhabditis elegans, functions as a hemichannel in thermosensory neurons and transmits temperature information from the thermosensory neurons to their postsynaptic interneurons. By monitoring neural activities in freely behaving animals, we find that hyperpolarizing thermosensory neurons inhibit the activity of the interneurons and that UNC-7 hemichannels regulate this process. UNC-7 is required to control thermotaxis behavior and functions independently of synaptic vesicle exocytosis. Our findings suggest that innexin hemichannels mediate neurotransmission from hyperpolarizing neurons in a manner that is distinct from the synaptic transmission, expanding the way of neural circuitry operations.
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Affiliation(s)
- Airi Nakayama
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
| | - Masakatsu Watanabe
- Laboratory of Pattern Formation, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka565-0871, Japan
| | - Riku Yamashiro
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
| | - Hiroo Kuroyanagi
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
| | - Hironori J. Matsuyama
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
| | - Atsunori Oshima
- Department of Basic Biology, Cellular and Structural Physiology Institute, Nagoya University, Chikusa, Nagoya464-8601, Japan
- Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Aichi464-8601, Japan
- Molecular Physiology Division, Institute for Glyco-core Research, Nagoya University, Chikusa-ku, Nagoya464-8601, Japan
- Division of Innovative Modality Development, Center for One Medicine Innovative Translational Research, Gifu University Institute for Advanced Study, Gifu501-11193, Japan
| | - Ikue Mori
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
- Chinese Institute for Brain Research, Changping District, Beijing102206, China
| | - Shunji Nakano
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
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Hong 洪卉 H, Moore LA, Apostolides PF, Trussell LO. Calcium-Sensitive Subthreshold Oscillations and Electrical Coupling in Principal Cells of Mouse Dorsal Cochlear Nucleus. J Neurosci 2024; 44:e0106202023. [PMID: 37968120 PMCID: PMC10860609 DOI: 10.1523/jneurosci.0106-20.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 11/02/2023] [Accepted: 11/08/2023] [Indexed: 11/17/2023] Open
Abstract
In higher sensory brain regions, slow oscillations (0.5-5 Hz) associated with quiet wakefulness and attention modulate multisensory integration, predictive coding, and perception. Although often assumed to originate via thalamocortical mechanisms, the extent to which subcortical sensory pathways are independently capable of slow oscillatory activity is unclear. We find that in the first station for auditory processing, the cochlear nucleus, fusiform cells from juvenile mice (of either sex) generate robust 1-2 Hz oscillations in membrane potential and exhibit electrical resonance. Such oscillations were absent prior to the onset of hearing, intrinsically generated by hyperpolarization-activated cyclic nucleotide-gated (HCN) and persistent Na+ conductances (NaP) interacting with passive membrane properties, and reflected the intrinsic resonance properties of fusiform cells. Cx36-containing gap junctions facilitated oscillation strength and promoted pairwise synchrony of oscillations between neighboring neurons. The strength of oscillations were strikingly sensitive to external Ca2+, disappearing at concentrations >1.7 mM, due in part to the shunting effect of small-conductance calcium-activated potassium (SK) channels. This effect explains their apparent absence in previous in vitro studies of cochlear nucleus which routinely employed high-Ca2+ extracellular solution. In contrast, oscillations were amplified in reduced Ca2+ solutions, due to relief of suppression by Ca2+ of Na+ channel gating. Our results thus reveal mechanisms for synchronous oscillatory activity in auditory brainstem, suggesting that slow oscillations, and by extension their perceptual effects, may originate at the earliest stages of sensory processing.
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Affiliation(s)
- Hui Hong 洪卉
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland 97239, Oregon
| | - Lucille A Moore
- Neuroscience Graduate Program, Oregon Health & Science University, Portland 97239, Oregon
| | - Pierre F Apostolides
- Neuroscience Graduate Program, Oregon Health & Science University, Portland 97239, Oregon
| | - Laurence O Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland 97239, Oregon
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7
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Valdebenito S, Ajasin D, Valerdi K, Liu YR, Rao S, Eugenin EA. Mechanisms of Intracellular Communication in Cancer and Pathogen Spreading. Results Probl Cell Differ 2024; 73:301-326. [PMID: 39242384 DOI: 10.1007/978-3-031-62036-2_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2024]
Abstract
Cell-to-cell interactions are essential for proper development, homeostasis, and complex syncytia/organ formation and function. Intercellular communication are mediated by multiple mechanisms including soluble mediators, adhesion molecules and specific mechanisms of cell to cell communication such as Gap junctions (GJ), tunneling nanotubes (TNT), and exosomes. Only recently, has been discovered that TNTs and exosomes enable the exchange of large signaling molecules, RNA, viral products, antigens, and organelles opening new avenues of research and therapeutic approaches. The focus of this review is to summarize these recent findings in physiologic and pathologic conditions.
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Affiliation(s)
- Silvana Valdebenito
- Department of Neurobiology, The University of Texas Medical Branch (UTMB), Galveston, TX, USA
| | - David Ajasin
- Department of Neurobiology, The University of Texas Medical Branch (UTMB), Galveston, TX, USA
| | - Karl Valerdi
- Department of Neurobiology, The University of Texas Medical Branch (UTMB), Galveston, TX, USA
| | | | - Samvrit Rao
- Thomas Jefferson High School for Science and Technology, Alexandria, VA, USA
| | - Eliseo A Eugenin
- Department of Neurobiology, The University of Texas Medical Branch (UTMB), Galveston, TX, USA.
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Abstract
The cerebellar cortex is an important system for relating neural circuits and learning. Its promise reflects the longstanding idea that it contains simple, repeated circuit modules with only a few cell types and a single plasticity mechanism that mediates learning according to classical Marr-Albus models. However, emerging data have revealed surprising diversity in neuron types, synaptic connections, and plasticity mechanisms, both locally and regionally within the cerebellar cortex. In light of these findings, it is not surprising that attempts to generate a holistic model of cerebellar learning across different behaviors have not been successful. While the cerebellum remains an ideal system for linking neuronal function with behavior, it is necessary to update the cerebellar circuit framework to achieve its great promise. In this review, we highlight recent advances in our understanding of cerebellar-cortical cell types, synaptic connections, signaling mechanisms, and forms of plasticity that enrich cerebellar processing.
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Affiliation(s)
- Court Hull
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, USA;
| | - Wade G Regehr
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA;
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Vaughn MJ, Haas JS. On the Diverse Functions of Electrical Synapses. Front Cell Neurosci 2022; 16:910015. [PMID: 35755782 PMCID: PMC9219736 DOI: 10.3389/fncel.2022.910015] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/25/2022] [Indexed: 11/13/2022] Open
Abstract
Electrical synapses are the neurophysiological product of gap junctional pores between neurons that allow bidirectional flow of current between neurons. They are expressed throughout the mammalian nervous system, including cortex, hippocampus, thalamus, retina, cerebellum, and inferior olive. Classically, the function of electrical synapses has been associated with synchrony, logically following that continuous conductance provided by gap junctions facilitates the reduction of voltage differences between coupled neurons. Indeed, electrical synapses promote synchrony at many anatomical and frequency ranges across the brain. However, a growing body of literature shows there is greater complexity to the computational function of electrical synapses. The paired membranes that embed electrical synapses act as low-pass filters, and as such, electrical synapses can preferentially transfer spike after hyperpolarizations, effectively providing spike-dependent inhibition. Other functions include driving asynchronous firing, improving signal to noise ratio, aiding in discrimination of dissimilar inputs, or dampening signals by shunting current. The diverse ways by which electrical synapses contribute to neuronal integration merits furthers study. Here we review how functions of electrical synapses vary across circuits and brain regions and depend critically on the context of the neurons and brain circuits involved. Computational modeling of electrical synapses embedded in multi-cellular models and experiments utilizing optical control and measurement of cellular activity will be essential in determining the specific roles performed by electrical synapses in varying contexts.
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Affiliation(s)
- Mitchell J Vaughn
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
| | - Julie S Haas
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
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Dorgans K, Guo D, Kurima K, Wickens J, Uusisaari MY. Designing AAV Vectors for Monitoring the Subtle Calcium Fluctuations of Inferior Olive Network in vivo. Front Cell Neurosci 2022; 16:825056. [PMID: 35573836 PMCID: PMC9093741 DOI: 10.3389/fncel.2022.825056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 03/21/2022] [Indexed: 11/13/2022] Open
Abstract
Adeno-associated viral (AAV) vectors, used as vehicles for gene transfer into the brain, are a versatile and powerful tool of modern neuroscience that allow identifying specific neuronal populations, monitoring and modulating their activity. For consistent and reproducible results, the AAV vectors must be engineered so that they reliably and accurately target cell populations. Furthermore, transgene expression must be adjusted to sufficient and safe levels compatible with the physiology of studied cells. We undertook the effort to identify and validate an AAV vector that could be utilized for researching the inferior olivary (IO) nucleus, a structure gating critical timing-related signals to the cerebellum. By means of systematic construct generation and quantitative expression profiling, we succeeded in creating a viral tool for specific and strong transfection of the IO neurons without adverse effects on their physiology. The potential of these tools is demonstrated by expressing the calcium sensor GCaMP6s in adult mouse IO neurons. We could monitor subtle calcium fluctuations underlying two signatures of intrinsic IO activity: the subthreshold oscillations (STOs) and the variable-duration action potential waveforms both in-vitro and in-vivo. Further, we show that the expression levels of GCaMP6s allowing such recordings are compatible with the delicate calcium-based dynamics of IO neurons, inviting future work into the network dynamics of the olivo-cerebellar system in behaving animals.
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Affiliation(s)
- Kevin Dorgans
- Neuronal Rhythms in Movement Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Da Guo
- Neuronal Rhythms in Movement Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Kiyoto Kurima
- Neurobiology Research Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Jeff Wickens
- Neurobiology Research Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Marylka Yoe Uusisaari
- Neuronal Rhythms in Movement Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- *Correspondence: Marylka Yoe Uusisaari
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Lang EJ, Handforth A. Is the inferior olive central to essential tremor? Yes. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2022; 163:133-165. [PMID: 35750361 PMCID: PMC11956747 DOI: 10.1016/bs.irn.2022.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We consider the question whether the inferior olive (IO) is required for essential tremor (ET). Much evidence shows that the olivocerebellar system is the main system capable of generating the widespread synchronous oscillatory Purkinje cell (PC) complex spike (CS) activity across the cerebellar cortex that would be capable of generating the type of bursting cerebellar output from the deep cerebellar nuclei (DCN) that could underlie tremor. Normally, synchronous CS activity primarily reflects the effective electrical coupling of IO neurons by gap junctions, and traditionally, ET research has focused on the hypothesis of increased coupling of IO neurons as the cause of hypersynchronous CS activity underlying tremor. However, recent pathology studies of brains from humans with ET and evidence from mutant mice, particularly the hotfoot17 mouse, that largely replicate the pathology of ET, suggest that the abnormal innervation of multiple Purkinje cells (PCs) by climbing fibers (Cfs) is related to tremor. In addition, ET brains show partial PC loss and axon terminal sprouting by surviving PCs. This may provide another mechanism for tremor. It is proposed that in ET, these three mechanisms may promote tremor. They all involve hypersynchronous DCN activity and an intact IO, but the level at which excessive synchronization occurs may be at the IO level (from abnormal afferent activity to this nucleus), the PC level (via aberrant Cfs), or the DCN level (via terminal PC collateral innervation).
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Affiliation(s)
- Eric J Lang
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University, New York, NY, United States.
| | - Adrian Handforth
- Neurology Service (W127), Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, United States
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Bellows S, Jimenez-Shahed J. Is essential tremor a disorder of GABA dysfunction? No. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2022; 163:285-310. [PMID: 35750366 DOI: 10.1016/bs.irn.2022.02.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Although essential tremor is common, its underlying pathophysiology remains uncertain, and several hypotheses seek to explain the tremor mechanism. The GABA hypothesis states that disinhibition of deep cerebellar neurons due to reduced GABAergic input from Purkinje cells results in increased pacemaker activity, leading to rhythmic output to the thalamo-cortical circuit and resulting in tremor. However, some neuroimaging, spectroscopy, and pathology studies have not shown a clear or consistent GABA deficiency in essential tremor, and animal models have indicated that large reductions of Purkinje cell inhibition may improve tremor. Instead, tremor is increasingly attributable to dysfunction in oscillating networks, where altered (but not necessarily reduced) inhibitory signaling can result in tremor. Hypersynchrony of Purkinje cell activity may account for excessive oscillatory cerebellar output, with potential contributions along multiple sites of the olivocerebellar loop. Although older animal tremor models, such as harmaline tremor, have explored contributions from the inferior olivary body, increasing evidence has pointed to the role of aberrant climbing fiber synaptic organization in oscillatory cerebellar activity and tremor generation. New animal models such as hotfoot17j mice, which exhibit abnormal climbing fiber organization due to mutations in Grid2, have recapitulated many features of ET. Similar abnormal climbing fiber architecture and excessive cerebellar oscillations as measured by EEG have been found in humans with essential tremor. Further understanding of hypersynchrony and excessive oscillatory activity in ET phenotypes may lead to more targeted and effective treatment options.
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13
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Function and Plasticity of Electrical Synapses in the Mammalian Brain: Role of Non-Junctional Mechanisms. BIOLOGY 2022; 11:biology11010081. [PMID: 35053079 PMCID: PMC8773336 DOI: 10.3390/biology11010081] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 12/30/2021] [Accepted: 12/31/2021] [Indexed: 01/27/2023]
Abstract
Simple Summary Relevant brain functions, such as perception, organization of behavior, and cognitive processes, are the outcome of information processing by neural circuits. Within these circuits, communication between neurons mainly relies on two modalities of synaptic transmission: chemical and electrical. Moreover, changes in the strength of these connections, aka synaptic plasticity, are believed to underlie processes of learning and memory, and its dysfunction has been suggested to underlie a variety of neurological disorders. While the relevance of chemical transmission and its plastic changes are known in great detail, analogous mechanisms and functional impact of their electrical counterparts were only recently acknowledged. In this article, we review the basic physical principles behind electrical transmission between neurons, the plethora of functional operations supported by this modality of neuron-to-neuron communication, as well as the basic principles of plasticity at these synapses. Abstract Electrical transmission between neurons is largely mediated by gap junctions. These junctions allow the direct flow of electric current between neurons, and in mammals, they are mostly composed of the protein connexin36. Circuits of electrically coupled neurons are widespread in these animals. Plus, experimental and theoretical evidence supports the notion that, beyond synchronicity, these circuits are able to perform sophisticated operations such as lateral excitation and inhibition, noise reduction, as well as the ability to selectively respond upon coincident excitatory inputs. Although once considered stereotyped and unmodifiable, we now know that electrical synapses are subject to modulation and, by reconfiguring neural circuits, these modulations can alter relevant operations. The strength of electrical synapses depends on the gap junction resistance, as well as on its functional interaction with the electrophysiological properties of coupled neurons. In particular, voltage and ligand gated channels of the non-synaptic membrane critically determine the efficacy of transmission at these contacts. Consistently, modulatory actions on these channels have been shown to represent relevant mechanisms of plasticity of electrical synaptic transmission. Here, we review recent evidence on the regulation of electrical synapses of mammals, the underlying molecular mechanisms, and the possible ways in which they affect circuit function.
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Baumel Y, Yamin HG, Cohen D. Cerebellar nuclei neurons display aberrant oscillations during harmaline-induced tremor. Heliyon 2021; 7:e08119. [PMID: 34660929 PMCID: PMC8503592 DOI: 10.1016/j.heliyon.2021.e08119] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/13/2021] [Accepted: 09/29/2021] [Indexed: 01/21/2023] Open
Abstract
Essential tremor, a common, debilitating motor disorder, is thought to be caused by cerebellar malfunction. It has been shown that rhythmic Purkinje cell firing is both necessary and sufficient to induce body tremor. During tremor, cerebellar nuclei (CN) cells also display oscillatory activity. This study examined whether rhythmic activity in the CN characterizes the occurrence of body tremor, or alternatively, whether aberrant bursting activity underlies body tremor. Cerebellar nuclei activity was chronically recorded and analyzed in freely moving and in harmaline treated rats. CN neurons displayed rhythmic activity in both conditions, but the number of oscillatory neurons and the relative oscillation time were significantly higher under harmaline. The dominant frequencies of the oscillations were broadly distributed under harmaline and the likelihood that two simultaneously recorded neurons would co-oscillate and their oscillation coherence were significantly lower. It is argued that these alterations rather than neuronal rhythmicity per se underlie harmaline-induced body tremor.
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Affiliation(s)
- Yuval Baumel
- The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Hagar G Yamin
- The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Dana Cohen
- The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, 52900, Israel
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15
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Choi U, Wang H, Hu M, Kim S, Sieburth D. Presynaptic coupling by electrical synapses coordinates a rhythmic behavior by synchronizing the activities of a neuron pair. Proc Natl Acad Sci U S A 2021; 118:e2022599118. [PMID: 33972428 PMCID: PMC8157971 DOI: 10.1073/pnas.2022599118] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Electrical synapses are specialized structures that mediate the flow of electrical currents between neurons and have well known roles in synchronizing the activities of neuronal populations, both by mediating the current transfer from more active to less active neurons and by shunting currents from active neurons to their less active neighbors. However, how these positive and negative functions of electrical synapses are coordinated to shape rhythmic synaptic outputs and behavior is not well understood. Here, using a combination of genetics, behavioral analysis, and live calcium imaging in Caenorhabditis elegans, we show that electrical synapses formed by the gap junction protein INX-1/innexin couple the presynaptic terminals of a pair of motor neurons (AVL and DVB) to synchronize their activation in response to a pacemaker signal. Live calcium imaging reveals that inx-1/innexin mutations lead to asynchronous activation of AVL and DVB, due, in part, to loss of AVL-mediated activation of DVB by the pacemaker. In addition, loss of inx-1 leads to the ectopic activation of DVB at inappropriate times during the cycle through the activation of the L-type voltage-gated calcium channel EGL-19. We propose that electrical synapses between AVL and DVB presynaptic terminals function to ensure the precise and robust execution of a specific step in a rhythmic behavior by both synchronizing the activities of presynaptic terminals in response to pacemaker signaling and by inhibiting their activation in between cycles when pacemaker signaling is low.
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Affiliation(s)
- Ukjin Choi
- Development, Stem Cell, and Regenerative Medicine Graduate Program, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033
| | - Han Wang
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033
| | - Mingxi Hu
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033
| | - Sungjin Kim
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033
| | - Derek Sieburth
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033;
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033
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16
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Wang G, Wu X. The potential antiepileptogenic effect of neuronal Cx36 gap junction channel blockage. Transl Neurosci 2021; 12:46-51. [PMID: 33604079 PMCID: PMC7876775 DOI: 10.1515/tnsci-2021-0008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 12/14/2020] [Accepted: 01/08/2021] [Indexed: 12/21/2022] Open
Abstract
Epilepsy is one of the most prevalent neurological disorders and can result in neuronal injury and degeneration. Consequently, research into new antiepileptic drugs capable of providing protection against neuronal injury and degeneration is extremely important. Neuronal Cx36 gap junction channels have been found to play an important role in epilepsy; thus, pharmacological interference using Cx36 gap junction channel blockers may be a promising strategy for disrupting the synchronization of neurons during seizure activity and protecting neurons. Based on these promising findings, several in vivo and in vitro studies are ongoing and the first encouraging results have been published. The results bring hope that neurons can be protected from injury and degeneration in patients with epilepsy, which is currently impossible.
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Affiliation(s)
- Guangliang Wang
- Department of Cardiology, Far Eastern Horizon Hospital, Linghai, Liaoning, People's Republic of China
| | - Xuemei Wu
- Department of Pediatric Neurology, First Hospital of Jilin University, 1 Xinmin Street, Changchun 130000, Jilin, People's Republic of China
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17
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Dorgans K, Kuhn B, Uusisaari MY. Imaging Subthreshold Voltage Oscillation With Cellular Resolution in the Inferior Olive in vitro. Front Cell Neurosci 2020; 14:607843. [PMID: 33381015 PMCID: PMC7767970 DOI: 10.3389/fncel.2020.607843] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 11/19/2020] [Indexed: 11/13/2022] Open
Abstract
Voltage imaging with cellular resolution in mammalian brain slices is still a challenging task. Here, we describe and validate a method for delivery of the voltage-sensitive dye ANNINE-6plus (A6+) into tissue for voltage imaging that results in higher signal-to-noise ratio (SNR) than conventional bath application methods. The not fully dissolved dye was injected into the inferior olive (IO) 0, 1, or 7 days prior to acute slice preparation using stereotactic surgery. We find that the voltage imaging improves after an extended incubation period in vivo in terms of labeled volume, homogeneous neuropil labeling with saliently labeled somata, and SNR. Preparing acute slices 7 days after the dye injection, the SNR is high enough to allow single-trial recording of IO subthreshold oscillations using wide-field (network-level) as well as high-magnification (single-cell level) voltage imaging with a CMOS camera. This method is easily adaptable to other brain regions where genetically-encoded voltage sensors are prohibitively difficult to use and where an ultrafast, pure electrochromic sensor, like A6+, is required. Due to the long-lasting staining demonstrated here, the method can be combined, for example, with deep-brain imaging using implantable GRIN lenses.
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Affiliation(s)
- Kevin Dorgans
- Neuronal Rhythms in Movement Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Bernd Kuhn
- Optical Neuroimaging Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Marylka Yoe Uusisaari
- Neuronal Rhythms in Movement Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
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18
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Li Q, Ma TL, Qiu YQ, Cui WQ, Chen T, Zhang WW, Wang J, Mao-Ying QL, Mi WL, Wang YQ, Chu YX. Connexin 36 Mediates Orofacial Pain Hypersensitivity Through GluK2 and TRPA1. Neurosci Bull 2020; 36:1484-1499. [PMID: 33067780 PMCID: PMC7719140 DOI: 10.1007/s12264-020-00594-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 09/06/2020] [Indexed: 12/15/2022] Open
Abstract
Trigeminal neuralgia is a debilitating condition, and the pain easily spreads to other parts of the face. Here, we established a mouse model of partial transection of the infraorbital nerve (pT-ION) and found that the Connexin 36 (Cx36) inhibitor mefloquine caused greater alleviation of pT-ION-induced cold allodynia compared to the reduction of mechanical allodynia. Mefloquine reversed the pT-ION-induced upregulation of Cx36, glutamate receptor ionotropic kainate 2 (GluK2), transient receptor potential ankyrin 1 (TRPA1), and phosphorylated extracellular signal regulated kinase (p-ERK) in the trigeminal ganglion. Cold allodynia but not mechanical allodynia induced by pT-ION or by virus-mediated overexpression of Cx36 in the trigeminal ganglion was reversed by the GluK2 antagonist NS102, and knocking down Cx36 expression in Nav1.8-expressing nociceptors by injecting virus into the orofacial skin area of Nav1.8-Cre mice attenuated cold allodynia but not mechanical allodynia. In conclusion, we show that Cx36 contributes greatly to the development of orofacial pain hypersensitivity through GluK2, TRPA1, and p-ERK signaling.
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Affiliation(s)
- Qian Li
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
| | - Tian-Le Ma
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
| | - You-Qi Qiu
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
| | - Wen-Qiang Cui
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
- Department of Pain Management, Shandong Provincial Qianfoshan Hospital, The First Hospital Affiliated with Shandong First Medical University, Jinan, 250000, China
| | - Teng Chen
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
| | - Wen-Wen Zhang
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
| | - Jing Wang
- Department of Nephropathy, The Third Affiliated Hospital of Shenzhen University, Luohu Hospital Group, Shenzhen, 518001, China
| | - Qi-Liang Mao-Ying
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
| | - Wen-Li Mi
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
| | - Yan-Qing Wang
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
| | - Yu-Xia Chu
- Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology, and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China.
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19
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Tetenborg S, Wang HY, Nemitz L, Depping A, Espejo AB, Aseervatham J, Bedford MT, Janssen-Bienhold U, O'Brien J, Dedek K. Phosphorylation of Connexin36 near the C-terminus switches binding affinities for PDZ-domain and 14-3-3 proteins in vitro. Sci Rep 2020; 10:18378. [PMID: 33110101 PMCID: PMC7592057 DOI: 10.1038/s41598-020-75375-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 10/12/2020] [Indexed: 12/20/2022] Open
Abstract
Connexin36 (Cx36) is the most abundant connexin in central nervous system neurons. It forms gap junction channels that act as electrical synapses. Similar to chemical synapses, Cx36-containing gap junctions undergo activity-dependent plasticity and complex regulation. Cx36 gap junctions represent multimolecular complexes and contain cytoskeletal, regulatory and scaffolding proteins, which regulate channel conductance, assembly and turnover. The amino acid sequence of mammalian Cx36 harbors a phosphorylation site for the Ca2+/calmodulin-dependent kinase II at serine 315. This regulatory site is homologous to the serine 298 in perch Cx35 and in close vicinity to a PDZ binding domain at the very C-terminal end of the protein. We hypothesized that this phosphorylation site may serve as a molecular switch, influencing the affinity of the PDZ binding domain for its binding partners. Protein microarray and pulldown experiments revealed that this is indeed the case: phosphorylation of serine 298 decreased the binding affinity for MUPP1, a known scaffolding partner of connexin36, and increased the binding affinity for two different 14-3-3 proteins. Although we did not find the same effect in cell culture experiments, our data suggest that phosphorylation of serine 315/298 may serve to recruit different proteins to connexin36/35-containing gap junctions in an activity-dependent manner.
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Affiliation(s)
- Stephan Tetenborg
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany
- Ruiz Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA
| | - Helen Y Wang
- Ruiz Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA
| | - Lena Nemitz
- Visual Neuroscience, Dept. of Neuroscience, University of Oldenburg, Oldenburg, Germany
| | - Anne Depping
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany
| | - Alexsandra B Espejo
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, TX, 78957, USA
| | - Jaya Aseervatham
- Ruiz Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA
| | - Mark T Bedford
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, TX, 78957, USA
| | - Ulrike Janssen-Bienhold
- Visual Neuroscience, Dept. of Neuroscience, University of Oldenburg, Oldenburg, Germany
- Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
| | - John O'Brien
- Ruiz Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA
| | - Karin Dedek
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany.
- Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany.
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20
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Handforth A, Lang EJ. Increased Purkinje Cell Complex Spike and Deep Cerebellar Nucleus Synchrony as a Potential Basis for Syndromic Essential Tremor. A Review and Synthesis of the Literature. THE CEREBELLUM 2020; 20:266-281. [PMID: 33048308 DOI: 10.1007/s12311-020-01197-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/29/2020] [Indexed: 12/19/2022]
Abstract
We review advances in understanding Purkinje cell (PC) complex spike (CS) physiology that suggest increased CS synchrony underlies syndromic essential tremor (ET). We searched PubMed for papers describing factors that affect CS synchrony or cerebellar circuits potentially related to tremor. Inferior olivary (IO) neurons are electrically coupled, with the degree of coupling controlled by excitatory and GABAergic inputs. Clusters of coupled IO neurons synchronize CSs within parasagittal bands via climbing fibers (Cfs). When motor cortex is stimulated in rats at varying frequencies, whisker movement occurs at ~10 Hz, correlated with synchronous CSs, indicating that the IO/CS oscillatory rhythm gates movement frequency. Intra-IO injection of the GABAA receptor antagonist picrotoxin increases CS synchrony, increases whisker movement amplitude, and induces tremor. Harmaline and 5-HT2a receptor activation also increase IO coupling and CS synchrony and induce tremor. The hotfoot17 mouse displays features found in ET brains, including cerebellar GluRδ2 deficiency and abnormal PC Cf innervation, with IO- and PC-dependent cerebellar oscillations and tremor likely due to enhanced CS synchrony. Heightened coupling within the IO oscillator leads, through its dynamic control of CS synchrony, to increased movement amplitude and, when sufficiently intense, action tremor. Increased CS synchrony secondary to aberrant Cf innervation of multiple PCs likely also underlies hotfoot17 tremor. Deep cerebellar nucleus (DCN) hypersynchrony may occur secondary to increased CS synchrony but might also occur from PC axonal terminal sprouting during partial PC loss. Through these combined mechanisms, increased CS/DCN synchrony may plausibly underlie syndromic ET.
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Affiliation(s)
- Adrian Handforth
- Neurology Service, Veterans Affairs Greater Los Angeles Healthcare System, 11301 Wilshire Blvd., Los Angeles, CA, 90073, USA.
| | - Eric J Lang
- Department of Neuroscience and Physiology, New York University, School of Medicine, New York, NY, USA
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21
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Dere D, Zlomuzica A, Dere E. Channels to consciousness: a possible role of gap junctions in consciousness. Rev Neurosci 2020; 32:/j/revneuro.ahead-of-print/revneuro-2020-0012/revneuro-2020-0012.xml. [PMID: 32853172 DOI: 10.1515/revneuro-2020-0012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 06/26/2020] [Indexed: 12/20/2022]
Abstract
The neurophysiological basis of consciousness is still unknown and one of the most challenging questions in the field of neuroscience and related disciplines. We propose that consciousness is characterized by the maintenance of mental representations of internal and external stimuli for the execution of cognitive operations. Consciousness cannot exist without working memory, and it is likely that consciousness and working memory share the same neural substrates. Here, we present a novel psychological and neurophysiological framework that explains the role of consciousness for cognition, adaptive behavior, and everyday life. A hypothetical architecture of consciousness is presented that is organized as a system of operation and storage units named platforms that are controlled by a consciousness center (central executive/online platform). Platforms maintain mental representations or contents, are entrusted with different executive functions, and operate at different levels of consciousness. The model includes conscious-mode central executive/online and mental time travel platforms and semiconscious steady-state and preconscious standby platforms. Mental representations or contents are represented by neural circuits and their support cells (astrocytes, oligodendrocytes, etc.) and become conscious when neural circuits reverberate, that is, fire sequentially and continuously with relative synchronicity. Reverberatory activity in neural circuits may be initiated and maintained by pacemaker cells/neural circuit pulsars, enhanced electronic coupling via gap junctions, and unapposed hemichannel opening. The central executive/online platform controls which mental representations or contents should become conscious by recruiting pacemaker cells/neural network pulsars, the opening of hemichannels, and promoting enhanced neural circuit coupling via gap junctions.
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Affiliation(s)
- Dorothea Dere
- Département UMR 8256 Adaptation Biologique et Vieillissement, Sorbonne Université, Institut de Biologie Paris-Seine, (IBPS), UFR des Sciences de la Vie, Campus Pierre et Marie Curie, Bâtiment B, 9 quai Saint Bernard, F-75005 Paris Cedex, France
| | - Armin Zlomuzica
- Faculty of Psychology, Behavioral and Clinical Neuroscience, University of Bochum, Massenbergstraße 9-13, D-44787 Bochum, Germany
| | - Ekrem Dere
- Département UMR 8256 Adaptation Biologique et Vieillissement, Sorbonne Université, Institut de Biologie Paris-Seine, (IBPS), UFR des Sciences de la Vie, Campus Pierre et Marie Curie, Bâtiment B, 9 quai Saint Bernard, F-75005 Paris Cedex, France
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22
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Electrical coupling controls dimensionality and chaotic firing of inferior olive neurons. PLoS Comput Biol 2020; 16:e1008075. [PMID: 32730255 PMCID: PMC7419012 DOI: 10.1371/journal.pcbi.1008075] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 08/11/2020] [Accepted: 06/18/2020] [Indexed: 01/15/2023] Open
Abstract
We previously proposed, on theoretical grounds, that the cerebellum must regulate the dimensionality of its neuronal activity during motor learning and control to cope with the low firing frequency of inferior olive neurons, which form one of two major inputs to the cerebellar cortex. Such dimensionality regulation is possible via modulation of electrical coupling through the gap junctions between inferior olive neurons by inhibitory GABAergic synapses. In addition, we previously showed in simulations that intermediate coupling strengths induce chaotic firing of inferior olive neurons and increase their information carrying capacity. However, there is no in vivo experimental data supporting these two theoretical predictions. Here, we computed the levels of synchrony, dimensionality, and chaos of the inferior olive code by analyzing in vivo recordings of Purkinje cell complex spike activity in three different coupling conditions: carbenoxolone (gap junctions blocker), control, and picrotoxin (GABA-A receptor antagonist). To examine the effect of electrical coupling on dimensionality and chaotic dynamics, we first determined the physiological range of effective coupling strengths between inferior olive neurons in the three conditions using a combination of a biophysical network model of the inferior olive and a novel Bayesian model averaging approach. We found that effective coupling co-varied with synchrony and was inversely related to the dimensionality of inferior olive firing dynamics, as measured via a principal component analysis of the spike trains in each condition. Furthermore, for both the model and the data, we found an inverted U-shaped relationship between coupling strengths and complexity entropy, a measure of chaos for spiking neural data. These results are consistent with our hypothesis according to which electrical coupling regulates the dimensionality and the complexity in the inferior olive neurons in order to optimize both motor learning and control of high dimensional motor systems by the cerebellum. Computational theory suggests that the cerebellum must decrease the dimensionality of its neuronal activity to learn and control high dimensional motor systems effectively, while being constrained by the low firing frequency of inferior olive neurons, one of the two major source of input signals to the cerebellum. We previously proposed that the cerebellum adaptively controls the dimensionality of inferior olive firing by adjusting the level of synchrony and that such control is made possible by modulating the electrical coupling strength between inferior olive neurons. Here, we developed a novel method that uses a biophysical model of the inferior olive to accurately estimate the effective coupling strengths between inferior olive neurons from in vivo recordings of spike activity in three different coupling conditions. We found that high coupling strengths induce synchronous firing and decrease the dimensionality of inferior olive firing dynamics. In contrast, intermediate coupling strengths lead to chaotic firing and increase the dimensionality of the firing dynamics. Thus, electrical coupling is a feasible mechanism to control dimensionality and chaotic firing of inferior olive neurons. In sum, our results provide insights into possible mechanisms underlying cerebellar function and, in general, a biologically plausible framework to control the dimensionality of neural coding.
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23
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Sánchez OF, Rodríguez AV, Velasco-España JM, Murillo LC, Sutachan JJ, Albarracin SL. Role of Connexins 30, 36, and 43 in Brain Tumors, Neurodegenerative Diseases, and Neuroprotection. Cells 2020; 9:E846. [PMID: 32244528 PMCID: PMC7226843 DOI: 10.3390/cells9040846] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 02/15/2020] [Accepted: 02/24/2020] [Indexed: 02/07/2023] Open
Abstract
Gap junction (GJ) channels and their connexins (Cxs) are complex proteins that have essential functions in cell communication processes in the central nervous system (CNS). Neurons, astrocytes, oligodendrocytes, and microglial cells express an extraordinary repertory of Cxs that are important for cell to cell communication and diffusion of metabolites, ions, neurotransmitters, and gliotransmitters. GJs and Cxs not only contribute to the normal function of the CNS but also the pathological progress of several diseases, such as cancer and neurodegenerative diseases. Besides, they have important roles in mediating neuroprotection by internal or external molecules. However, regulation of Cx expression by epigenetic mechanisms has not been fully elucidated. In this review, we provide an overview of the known mechanisms that regulate the expression of the most abundant Cxs in the central nervous system, Cx30, Cx36, and Cx43, and their role in brain cancer, CNS disorders, and neuroprotection. Initially, we focus on describing the Cx gene structure and how this is regulated by epigenetic mechanisms. Then, the posttranslational modifications that mediate the activity and stability of Cxs are reviewed. Finally, the role of GJs and Cxs in glioblastoma, Alzheimer's, Parkinson's, and Huntington's diseases, and neuroprotection are analyzed with the aim of shedding light in the possibility of using Cx regulators as potential therapeutic molecules.
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Affiliation(s)
- Oscar F. Sánchez
- Department of Nutrition and Biochemistry, Pontificia Universidad Javeriana, 110911 Bogota, Colombia; (A.V.R.); (J.M.V.-E.); (L.C.M.); (J.-J.S.)
| | | | | | | | | | - Sonia-Luz Albarracin
- Department of Nutrition and Biochemistry, Pontificia Universidad Javeriana, 110911 Bogota, Colombia; (A.V.R.); (J.M.V.-E.); (L.C.M.); (J.-J.S.)
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24
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Mitoma H, Buffo A, Gelfo F, Guell X, Fucà E, Kakei S, Lee J, Manto M, Petrosini L, Shaikh AG, Schmahmann JD. Consensus Paper. Cerebellar Reserve: From Cerebellar Physiology to Cerebellar Disorders. CEREBELLUM (LONDON, ENGLAND) 2020; 19:131-153. [PMID: 31879843 PMCID: PMC6978437 DOI: 10.1007/s12311-019-01091-9] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cerebellar reserve refers to the capacity of the cerebellum to compensate for tissue damage or loss of function resulting from many different etiologies. When the inciting event produces acute focal damage (e.g., stroke, trauma), impaired cerebellar function may be compensated for by other cerebellar areas or by extracerebellar structures (i.e., structural cerebellar reserve). In contrast, when pathological changes compromise cerebellar neuronal integrity gradually leading to cell death (e.g., metabolic and immune-mediated cerebellar ataxias, neurodegenerative ataxias), it is possible that the affected area itself can compensate for the slowly evolving cerebellar lesion (i.e., functional cerebellar reserve). Here, we examine cerebellar reserve from the perspective of the three cornerstones of clinical ataxiology: control of ocular movements, coordination of voluntary axial and appendicular movements, and cognitive functions. Current evidence indicates that cerebellar reserve is potentiated by environmental enrichment through the mechanisms of autophagy and synaptogenesis, suggesting that cerebellar reserve is not rigid or fixed, but exhibits plasticity potentiated by experience. These conclusions have therapeutic implications. During the period when cerebellar reserve is preserved, treatments should be directed at stopping disease progression and/or limiting the pathological process. Simultaneously, cerebellar reserve may be potentiated using multiple approaches. Potentiation of cerebellar reserve may lead to compensation and restoration of function in the setting of cerebellar diseases, and also in disorders primarily of the cerebral hemispheres by enhancing cerebellar mechanisms of action. It therefore appears that cerebellar reserve, and the underlying plasticity of cerebellar microcircuitry that enables it, may be of critical neurobiological importance to a wide range of neurological/neuropsychiatric conditions.
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Affiliation(s)
- H Mitoma
- Medical Education Promotion Center, Tokyo Medical University, Tokyo, Japan.
| | - A Buffo
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, 10126, Turin, Italy
- Neuroscience Institute Cavalieri Ottolenghi, 10043, Orbassano, Italy
| | - F Gelfo
- Department of Human Sciences, Guglielmo Marconi University, 00193, Rome, Italy
- IRCCS Fondazione Santa Lucia, 00179, Rome, Italy
| | - X Guell
- Department of Neurology, Massachusetts General Hospital, Ataxia Unit, Cognitive Behavioral Neurology Unit, Laboratory for Neuroanatomy and Cerebellar Neurobiology, Harvard Medical School, Boston, USA
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, USA
| | - E Fucà
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, 10126, Turin, Italy
- Neuroscience Institute Cavalieri Ottolenghi, 10043, Orbassano, Italy
- Child and Adolescent Neuropsychiatry Unit, Bambino Gesù Children's Hospital, 00165, Rome, Italy
| | - S Kakei
- Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - J Lee
- Komatsu University, Komatsu, Japan
| | - M Manto
- Unité des Ataxies Cérébelleuses, Service de Neurologie, CHU-Charleroi, 6000, Charleroi, Belgium
- Service des Neurosciences, University of Mons, 7000, Mons, Belgium
| | - L Petrosini
- IRCCS Fondazione Santa Lucia, 00179, Rome, Italy
| | - A G Shaikh
- Louis Stokes Cleveland VA Medical Center, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - J D Schmahmann
- Department of Neurology, Massachusetts General Hospital, Ataxia Unit, Cognitive Behavioral Neurology Unit, Laboratory for Neuroanatomy and Cerebellar Neurobiology, Harvard Medical School, Boston, USA
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25
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Chang TP, Gold DR, Otero-Millan J, Huang BR, Zee DS. Pendular Oscillation and Ocular Bobbing After Pontine Hemorrhage. THE CEREBELLUM 2019; 20:734-743. [PMID: 31883062 DOI: 10.1007/s12311-019-01086-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The pathophysiology of acute, vertical spontaneous eye movements following pontine hemorrhage is not well understood. Here, we present and discuss the video-oculography findings of a patient with acute pontine hemorrhage who developed vertical pendular oscillation and ocular bobbing while comatose. The amplitudes, peak velocities, frequency distribution, and phase planes (velocity versus position) of the eye movements were analyzed. The vertical pendular oscillation was rhythmic with a peak frequency of 1.7 Hz, but amplitudes (mean 1.9°, range 0.2-8.2°) and peak velocities (mean 20.6°/s; range 5.9-60.6°/sec) fluctuated. Overall, their peak velocities were asymmetric, faster with downward than upward. Higher peak velocities were seen with larger amplitudes (downward phase r = 0.95, p < 0.001; upward phase r = 0.91, p < 0.001) and with movements beginning at eye positions lower in the orbit (downward phase r = - 0.64, p < 0.001; upward phase r = - 0.86, p < 0.001). Interspersed were typical ocular bobbing waveforms with a fast (peak velocity 128.8°/s), large-amplitude (17.5°) downward movement, sometimes followed by a flat interphase interval (0.5 s) when the eye was nearly stationary, and then a slow return to mid-position with a decaying velocity waveform. To account for the presence and co-existence of pendular oscillations and bobbing, we present and discuss three hypothetical models, not necessarily mutually exclusive: (1) oscillations originating in the inferior olives due to disruption of the central tegmental tract(s); (2) unstable neural integrator function due to pontine cell group damage involving neurons involved in gaze-holding; (3) low-frequency saccadic intrusions following omnipause neuron damage.
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Affiliation(s)
- Tzu-Pu Chang
- Department of Neurology, Neuro-medical Scientific Center, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, No. 88, Sec.1, Fengxing Rd., Tanzi Dist., Taichung City, 42743, Taiwan.,Department of Neurology, School of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Daniel R Gold
- Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St Pathology 2-210, Baltimore, MD, 21287, USA
| | - Jorge Otero-Millan
- Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St Pathology 2-210, Baltimore, MD, 21287, USA
| | - Bor-Ren Huang
- Department of Neurosurgery, Neuro-medical Scientific Center, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan.,Department of Neurosurgery, School of Medicine, Tzu Chi University, No. 88, Sec.1, Fengxing Rd., Tanzi Dist, Taichung City, 42743, Taiwan
| | - David S Zee
- Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St Pathology 2-210, Baltimore, MD, 21287, USA.
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26
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Kuo SH, Louis ED, Faust PL, Handforth A, Chang SY, Avlar B, Lang EJ, Pan MK, Miterko LN, Brown AM, Sillitoe RV, Anderson CJ, Pulst SM, Gallagher MJ, Lyman KA, Chetkovich DM, Clark LN, Tio M, Tan EK, Elble RJ. Current Opinions and Consensus for Studying Tremor in Animal Models. CEREBELLUM (LONDON, ENGLAND) 2019; 18:1036-1063. [PMID: 31124049 PMCID: PMC6872927 DOI: 10.1007/s12311-019-01037-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Tremor is the most common movement disorder; however, we are just beginning to understand the brain circuitry that generates tremor. Various neuroimaging, neuropathological, and physiological studies in human tremor disorders have been performed to further our knowledge of tremor. But, the causal relationship between these observations and tremor is usually difficult to establish and detailed mechanisms are not sufficiently studied. To overcome these obstacles, animal models can provide an important means to look into human tremor disorders. In this manuscript, we will discuss the use of different species of animals (mice, rats, fruit flies, pigs, and monkeys) to model human tremor disorders. Several ways to manipulate the brain circuitry and physiology in these animal models (pharmacology, genetics, and lesioning) will also be discussed. Finally, we will discuss how these animal models can help us to gain knowledge of the pathophysiology of human tremor disorders, which could serve as a platform towards developing novel therapies for tremor.
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Affiliation(s)
- Sheng-Han Kuo
- Department of Neurology, Columbia University, 650 West 168th Street, Room 305, New York, NY, 10032, USA.
| | - Elan D Louis
- Department of Neurology, Yale School of Medicine, Yale University, 800 Howard Avenue, Ste Lower Level, New Haven, CT, 06519, USA.
- Department of Chronic Disease Epidemiology, Yale School of Public Health, Yale University, New Haven, CT, USA.
- Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, CT, USA.
| | - Phyllis L Faust
- Department of Pathology and Cell Biology, Columbia University Medical Center and the New York Presbyterian Hospital, New York, NY, USA
| | - Adrian Handforth
- Neurology Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA
| | - Su-Youne Chang
- Department of Neurologic Surgery and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | - Billur Avlar
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY, USA
| | - Eric J Lang
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY, USA
| | - Ming-Kai Pan
- Department of Medical Research and Neurology, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Lauren N Miterko
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute of Texas Children's Hospital, Houston, TX, USA
| | - Amanda M Brown
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute of Texas Children's Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Roy V Sillitoe
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute of Texas Children's Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Collin J Anderson
- Department of Neurology, University of Utah, Salt Lake City, UT, USA
| | - Stefan M Pulst
- Department of Neurology, University of Utah, Salt Lake City, UT, USA
| | | | - Kyle A Lyman
- Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | | | - Lorraine N Clark
- Department of Pathology and Cell Biology, Columbia University Medical Center and the New York Presbyterian Hospital, New York, NY, USA
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Murni Tio
- Department of Neurology, National Neuroscience Institute, Singapore, Singapore
- Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Eng-King Tan
- Department of Neurology, National Neuroscience Institute, Singapore, Singapore
- Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Rodger J Elble
- Department of Neurology, Southern Illinois University School of Medicine, Springfield, IL, USA
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27
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Lee J, Jo HJ, Kim I, Lee J, Min HK, In MH, Knight EJ, Chang SY. Mapping BOLD Activation by Pharmacologically Evoked Tremor in Swine. Front Neurosci 2019; 13:985. [PMID: 31619955 PMCID: PMC6759958 DOI: 10.3389/fnins.2019.00985] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 09/02/2019] [Indexed: 11/26/2022] Open
Abstract
Harmaline-induced tremor is one of the most commonly utilized disease models for essential tremor (ET). However, the underlying neural networks involved in harmaline-induced tremor and the degree to which these are a representative model of the pathophysiologic mechanism of ET are incompletely understood. In this study, we evaluated the functional brain network effects induced by systemic injection of harmaline using pharmacological functional magnetic resonance imaging (ph-fMRI) in the swine model. With harmaline administration, we observed significant activation changes in cerebellum, thalamus, and inferior olivary nucleus (ION). In addition, inter-regional correlations in activity between cerebellum and deep cerebellar nuclei and between cerebellum and thalamus were significantly enhanced. These harmaline-induced effects gradually decreased with repeated administration of drug, replicating the previously demonstrated ‘tolerance’ effect. This study demonstrates that harmaline-induced tremor is associated with activity changes in brain regions previously implicated in humans with ET. Thus, harmaline-induction of tremor in the swine may be a useful model to explore the neurological effects of novel therapeutic agents and/or neuromodulation techniques for ET.
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Affiliation(s)
- Jeyeon Lee
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, United States
| | - Hang Joon Jo
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, United States.,Department of Radiology, Mayo Clinic, Rochester, MN, United States.,Department of Neurology, Mayo Clinic, Rochester, MN, United States.,Department of Physiology, College of Medicine, Hanyang University, Seoul, South Korea
| | - Inyong Kim
- Department of Neurology, Mayo Clinic, Rochester, MN, United States
| | - Jihyun Lee
- Laboratory of Brain and Cognitive Sciences for Convergence Medicine, Hallym University College of Medicine, Anyang, South Korea
| | - Hoon-Ki Min
- Department of Radiology, Mayo Clinic, Rochester, MN, United States
| | - Myung-Ho In
- Department of Radiology, Mayo Clinic, Rochester, MN, United States
| | - Emily J Knight
- Department of Developmental Behavioral Pediatrics, University of Rochester, Rochester, NY, United States
| | - Su-Youne Chang
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, United States.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
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28
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Papapetropoulos S, Lee MS, Boyer S, Newbold EJ. A Phase 2, Randomized, Double-Blind, Placebo-Controlled Trial of CX-8998, a Selective Modulator of the T-Type Calcium Channel in Inadequately Treated Moderate to Severe Essential Tremor: T-CALM Study Design and Methodology for Efficacy Endpoint and Digital Biomarker Selection. Front Neurol 2019; 10:597. [PMID: 31244760 PMCID: PMC6579833 DOI: 10.3389/fneur.2019.00597] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 05/21/2019] [Indexed: 11/13/2022] Open
Abstract
Background: Essential tremor (ET) is a common, progressive neurological syndrome with bilateral upper-limb dysfunction of at least 3-year duration, with or without tremor in other body locations. This disorder has a negative impact on daily function and quality of life. A single oral therapy has been approved by FDA for ET. Off-label pharmacotherapies have inadequate efficacy and poor tolerability with high rates of patient dissatisfaction and discontinuation. Safe and efficacious pharmacotherapies are urgently needed to decrease tremor and improve daily living. T-CALM (Tremor-CAv3 modulation) protocol is designed to assess safety and efficacy of CX-8998, a selective modulator of the T-type calcium channel, for ET therapy. Methods/Design: T-CALM is a phase 2, proof of concept, randomized, double-blind, placebo-controlled trial. Titrated doses of CX-8998 to 10 mg BID or placebo will be administered for 28 days to moderate to severe ET patients who are inadequately treated with existing therapies. The primary endpoint will be change from baseline to day 28 of The Essential Tremor Rating Assessment Performance Subscale (TETRAS-PS). Secondary efficacy endpoints for clinician and patient perception of daily function will include TETRAS Activity of Daily Living (ADL), Quality of Life in Essential Tremor Questionnaire (QUEST), Clinical Global Impression-Improvement (CGI-I), Patient Global Impression of Change (PGIC), and Goal Attainment Scale (GAS). Kinesia One, Kinesia 360, and iMotor will biometrically evaluate motor function and tremor amplitude. Safety will be assessed by adverse events, physical and neurological exams and laboratory tests. Sample size of 43 patients per group is estimated to have 90% power to detect a 5.5-point difference between CX-8998 and placebo for TETRAS-PS. Efficacy analyses will be performed with covariance (ANCOVA) and 2-sided test at 0.05 significance level. Discussion: T-CALM has a unique design with physician rating scales, patient-focused questionnaires and scales and objective motor measurements to assess clinically meaningful and congruent efficacy. Patient perception of ET debilitation and therapy with CX-8998 will be key findings. Overall goal of T-CALM is generation of safety and efficacy data to support a go, no-go decision to further develop CX-8998 for ET. Design of T-CALM may guide future clinical studies of ET pharmacotherapies. Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT03101241
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29
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Geminiani A, Casellato C, D'Angelo E, Pedrocchi A. Complex Electroresponsive Dynamics in Olivocerebellar Neurons Represented With Extended-Generalized Leaky Integrate and Fire Models. Front Comput Neurosci 2019; 13:35. [PMID: 31244635 PMCID: PMC6563830 DOI: 10.3389/fncom.2019.00035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 05/20/2019] [Indexed: 11/24/2022] Open
Abstract
The neurons of the olivocerebellar circuit exhibit complex electroresponsive dynamics, which are thought to play a fundamental role for network entraining, plasticity induction, signal processing, and noise filtering. In order to reproduce these properties in single-point neuron models, we have optimized the Extended-Generalized Leaky Integrate and Fire (E-GLIF) neuron through a multi-objective gradient-based algorithm targeting the desired input–output relationships. In this way, E-GLIF was tuned toward the unique input–output properties of Golgi cells, granule cells, Purkinje cells, molecular layer interneurons, deep cerebellar nuclei cells, and inferior olivary cells. E-GLIF proved able to simulate the complex cell-specific electroresponsive dynamics of the main olivocerebellar neurons including pacemaking, adaptation, bursting, post-inhibitory rebound excitation, subthreshold oscillations, resonance, and phase reset. The integration of these E-GLIF point-neuron models into olivocerebellar Spiking Neural Networks will allow to evaluate the impact of complex electroresponsive dynamics at the higher scales, up to motor behavior, in closed-loop simulations of sensorimotor tasks.
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Affiliation(s)
- Alice Geminiani
- NEARLab, Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy
| | - Claudia Casellato
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Egidio D'Angelo
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Alessandra Pedrocchi
- NEARLab, Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy
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30
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Nakagawa N, Hosoya T. Slow Dynamics in Microcolumnar Gap Junction Network of Developing Neocortical Pyramidal Neurons. Neuroscience 2019; 406:554-562. [PMID: 30794844 DOI: 10.1016/j.neuroscience.2019.02.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 12/24/2018] [Accepted: 02/11/2019] [Indexed: 10/27/2022]
Abstract
Gap junctions mediate electrical coupling between neurons and modulate their firing activity. In mouse neocortical layer 5, the major types of pyramidal neurons organize into cell type-specific microcolumns that exhibit modular neuronal activity. During cortical development, microcolumn neurons are electrically coupled in a cell type-specific manner at the stage of synaptogenesis, forming a dense network of gap junctions. However, modulation of neuronal activity by the gap junction network has not been examined. Here, we show that the electrical coupling induces amplification and slow synchronization of action potentials. This slow synchronization is mediated by electrical transmission that is an order of magnitude slower than that of gap junction-coupled neurons of other types. Theoretical and structural analyses suggested that apical dendrites are a major site of electrical coupling, providing slow electrical transmission. These results suggest that the gap junction network organizes neuronal activity of developing cortical circuit modules with unique slow dynamics.
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Affiliation(s)
- Nao Nakagawa
- RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan.
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31
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Alcamí P, Pereda AE. Beyond plasticity: the dynamic impact of electrical synapses on neural circuits. Nat Rev Neurosci 2019; 20:253-271. [PMID: 30824857 DOI: 10.1038/s41583-019-0133-5] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Electrical synapses are found in vertebrate and invertebrate nervous systems. The cellular basis of these synapses is the gap junction, a group of intercellular channels that mediate direct communication between adjacent neurons. Similar to chemical synapses, electrical connections are modifiable and their variations in strength provide a mechanism for reconfiguring neural circuits. In addition, electrical synapses dynamically regulate neural circuits through properties without equivalence in chemical transmission. Because of their continuous nature and bidirectionality, electrical synapses allow electrical currents underlying changes in membrane potential to leak to 'coupled' partners, dampening neuronal excitability and altering their integrative properties. Remarkably, this effect can be transiently alleviated when comparable changes in membrane potential simultaneously occur in each of the coupled neurons, a phenomenon that is dynamically dictated by the timing of arriving signals such as synaptic potentials. By way of this mechanism, electrical synapses influence synaptic integration and action potential generation, imparting an additional layer of dynamic complexity to neural circuits.
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Affiliation(s)
- Pepe Alcamí
- Max Planck Institute for Ornithology, Seewiesen, Germany
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universitaet Munich, Martinsried, Germany
- Marine Biological Laboratory, Woods Hole, MA, USA
| | - Alberto E Pereda
- Marine Biological Laboratory, Woods Hole, MA, USA.
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.
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32
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Vrieler N, Loyola S, Yarden-Rabinowitz Y, Hoogendorp J, Medvedev N, Hoogland TM, De Zeeuw CI, De Schutter E, Yarom Y, Negrello M, Torben-Nielsen B, Uusisaari MY. Variability and directionality of inferior olive neuron dendrites revealed by detailed 3D characterization of an extensive morphological library. Brain Struct Funct 2019; 224:1677-1695. [PMID: 30929054 PMCID: PMC6509097 DOI: 10.1007/s00429-019-01859-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 03/09/2019] [Indexed: 12/14/2022]
Abstract
The inferior olive (IO) is an evolutionarily conserved brain stem structure and its output activity plays a major role in the cerebellar computation necessary for controlling the temporal accuracy of motor behavior. The precise timing and synchronization of IO network activity has been attributed to the dendro-dendritic gap junctions mediating electrical coupling within the IO nucleus. Thus, the dendritic morphology and spatial arrangement of IO neurons governs how synchronized activity emerges in this nucleus. To date, IO neuron structural properties have been characterized in few studies and with small numbers of neurons; these investigations have described IO neurons as belonging to two morphologically distinct types, “curly” and “straight”. In this work we collect a large number of individual IO neuron morphologies visualized using different labeling techniques and present a thorough examination of their morphological properties and spatial arrangement within the olivary neuropil. Our results show that the extensive heterogeneity in IO neuron dendritic morphologies occupies a continuous range between the classically described “curly” and “straight” types, and that this continuum is well represented by a relatively simple measure of “straightness”. Furthermore, we find that IO neuron dendritic trees are often directionally oriented. Combined with an examination of cell body density distributions and dendritic orientation of adjacent IO neurons, our results suggest that the IO network may be organized into groups of densely coupled neurons interspersed with areas of weaker coupling.
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Affiliation(s)
- Nora Vrieler
- Department of Neurobiology, Institute of Life Sciences and Edmond and Lily Safra Center for Brain Sciences, Hebrew University, Jerusalem, Israel
| | - Sebastian Loyola
- Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands.,Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands
| | - Yasmin Yarden-Rabinowitz
- Department of Neurobiology, Institute of Life Sciences and Edmond and Lily Safra Center for Brain Sciences, Hebrew University, Jerusalem, Israel
| | - Jesse Hoogendorp
- Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Nikolay Medvedev
- Computational Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan
| | - Tycho M Hoogland
- Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands.,Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands
| | - Chris I De Zeeuw
- Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands.,Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands
| | - Erik De Schutter
- Computational Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan
| | - Yosef Yarom
- Department of Neurobiology, Institute of Life Sciences and Edmond and Lily Safra Center for Brain Sciences, Hebrew University, Jerusalem, Israel
| | - Mario Negrello
- Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands
| | | | - Marylka Yoe Uusisaari
- Neuronal Rhythms in Movement Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan.
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33
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Abudara V, Retamal MA, Del Rio R, Orellana JA. Synaptic Functions of Hemichannels and Pannexons: A Double-Edged Sword. Front Mol Neurosci 2018; 11:435. [PMID: 30564096 PMCID: PMC6288452 DOI: 10.3389/fnmol.2018.00435] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/08/2018] [Indexed: 01/18/2023] Open
Abstract
The classical view of synapses as the functional contact between presynaptic and postsynaptic neurons has been challenged in recent years by the emerging regulatory role of glial cells. Astrocytes, traditionally considered merely supportive elements are now recognized as active modulators of synaptic transmission and plasticity at the now so-called "tripartite synapse." In addition, an increasing body of evidence indicates that beyond immune functions microglia also participate in various processes aimed to shape synaptic plasticity. Release of neuroactive compounds of glial origin, -process known as gliotransmission-, constitute a widespread mechanism through which glial cells can either potentiate or reduce the synaptic strength. The prevailing vision states that gliotransmission depends on an intracellular Ca2+/exocytotic-mediated release; notwithstanding, growing evidence is pointing at hemichannels (connexons) and pannexin channels (pannexons) as alternative non-vesicular routes for gliotransmitters efflux. In concurrence with this novel concept, both hemichannels and pannexons are known to mediate the transfer of ions and signaling molecules -such as ATP and glutamate- between the cytoplasm and the extracellular milieu. Importantly, recent reports show that glial hemichannels and pannexons are capable to perceive synaptic activity and to respond to it through changes in their functional state. In this article, we will review the current information supporting the "double edge sword" role of hemichannels and pannexons in the function of central and peripheral synapses. At one end, available data support the idea that these channels are chief components of a feedback control mechanism through which gliotransmitters adjust the synaptic gain in either resting or stimulated conditions. At the other end, we will discuss how the excitotoxic release of gliotransmitters and [Ca2+]i overload linked to the opening of hemichannels/pannexons might impact cell function and survival in the nervous system.
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Affiliation(s)
- Verónica Abudara
- Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile.,Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States.,Programa de Comunicación Celular en Cáncer, Instituto de Ciencias e Innovación en Medicina, Santiago, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
| | - Juan A Orellana
- Departamento de Neurología, Escuela de Medicina and Centro Interdisciplinario de Neurociencias, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Investigación y Estudio del Consumo de Alcohol en Adolescentes, Santiago, Chile
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34
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Kobayakawa Y, Masaki K, Yamasaki R, Shiraishi W, Hayashida S, Hayashi S, Okamoto K, Matsushita T, Kira JI. Downregulation of Neuronal and Dendritic Connexin36-Made Electrical Synapses Without Glutamatergic Axon Terminals in Spinal Anterior Horn Cells From the Early Stage of Amyotrophic Lateral Sclerosis. Front Neurosci 2018; 12:894. [PMID: 30546295 PMCID: PMC6279874 DOI: 10.3389/fnins.2018.00894] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 11/15/2018] [Indexed: 11/13/2022] Open
Abstract
Connexin36 (Cx36) forms gap junctions between neurons, which are called electrical synapses, enabling adjacent neurons to communicate directly. The participation of chemical synapses in neurodegeneration in amyotrophic lateral sclerosis (ALS) has long been indicated, but it remains unclear whether electrical synapses are involved in the pathogenesis of ALS. We performed extensive immunopathological analyses using mutant superoxide dismutase 1 (SOD1G93A) transgenic mice and their littermates to investigate whether Cx36-made electrical synapses are affected in motor neuron diseases. We found that in the lamina IX of the lumbar spinal cord from wild type mice, about half of the Cx36 puncta existed independently of chemical synapse markers, while the rest coexisted with chemical synapse markers, such as vesicular glutamate transporter 1 (VGLUT1), which is a glutamatergic axon terminal marker, and/or glutamate decarboxylase 65 (GAD65), which is a GABAergic axon terminal marker. Cx36 single or Cx36/GAD65 double positive puncta, but not VGLUT1-containing puncta, were preferentially decreased on neuronal and dendritic surfaces of the anterior horn cells in the early stage of SOD1G93A ALS mice. Moreover, in five human autopsied sporadic ALS cases with bulbar or upper limb onset, Cx36 immunoreactivity was diminished in the proximal dendrites and neuropils of well-preserved large motor neurons in the lumbar anterior horns. These findings suggest that downregulation of neuronal and dendritic Cx36 in the spinal anterior horns commonly occurs from the early stage of hereditary and sporadic ALS. Cx36-made electrical synapses without glutamatergic signaling appear to be more vulnerable than other chemical synapses and electrical synapses with glutamatergic signaling in the early stage of motor neuron degeneration, suggesting involvement of Cx36-made electrical synapses in the pathogenesis of human ALS.
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Affiliation(s)
- Yuko Kobayakawa
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Katsuhisa Masaki
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Ryo Yamasaki
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Wataru Shiraishi
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Shotaro Hayashida
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Shintaro Hayashi
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Koichi Okamoto
- Department of Neurology, Geriatrics Research Institute and Hospital, Gunma, Japan
| | - Takuya Matsushita
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Jun-Ichi Kira
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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35
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Delmar M, Laird DW, Naus CC, Nielsen MS, Verselis VK, White TW. Connexins and Disease. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a029348. [PMID: 28778872 DOI: 10.1101/cshperspect.a029348] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Inherited or acquired alterations in the structure and function of connexin proteins have long been associated with disease. In the present work, we review current knowledge on the role of connexins in diseases associated with the heart, nervous system, cochlea, and skin, as well as cancer and pleiotropic syndromes such as oculodentodigital dysplasia (ODDD). Although incomplete by virtue of space and the extent of the topic, this review emphasizes the fact that connexin function is not only associated with gap junction channel formation. As such, both canonical and noncanonical functions of connexins are fundamental components in the pathophysiology of multiple connexin related disorders, many of them highly debilitating and life threatening. Improved understanding of connexin biology has the potential to advance our understanding of mechanisms, diagnosis, and treatment of disease.
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Affiliation(s)
- Mario Delmar
- The Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, New York 10016
| | - Dale W Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A5C1, Canada
| | - Christian C Naus
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Morten S Nielsen
- Department of Biological Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark
| | - Vytautas K Verselis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, New York 10461
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11790
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Abstract
Cortical oscillations are thought to be involved in many cognitive functions and processes. Several mechanisms have been proposed to regulate oscillations. One prominent but understudied mechanism is gap junction coupling. Gap junctions are ubiquitous in cortex between GABAergic interneurons. Moreover, recent experiments indicate their strength can be modified in an activity-dependent manner, similar to chemical synapses. We hypothesized that activity-dependent gap junction plasticity acts as a mechanism to regulate oscillations in the cortex. We developed a computational model of gap junction plasticity in a recurrent cortical network based on recent experimental findings. We showed that gap junction plasticity can serve as a homeostatic mechanism for oscillations by maintaining a tight balance between two network states: asynchronous irregular activity and synchronized oscillations. This homeostatic mechanism allows for robust communication between neuronal assemblies through two different mechanisms: transient oscillations and frequency modulation. This implies a direct functional role for gap junction plasticity in information transmission in cortex.
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Affiliation(s)
- Guillaume Pernelle
- Bioengineering Department, Imperial College London, London, United Kingdom
| | - Wilten Nicola
- Bioengineering Department, Imperial College London, London, United Kingdom
| | - Claudia Clopath
- Bioengineering Department, Imperial College London, London, United Kingdom
- * E-mail:
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Cheron J, Cheron G. Beta-gamma burst stimulations of the inferior olive induce high-frequency oscillations in the deep cerebellar nuclei. Eur J Neurosci 2018; 48:2879-2889. [PMID: 29460990 DOI: 10.1111/ejn.13873] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Revised: 02/12/2018] [Accepted: 02/13/2018] [Indexed: 11/30/2022]
Abstract
The cerebellum displays various sorts of rhythmic activities covering both low- and high-frequency oscillations. These cerebellar high-frequency oscillations were observed in the cerebellar cortex. Here, we hypothesised that not only is the cerebellar cortex a generator of high-frequency oscillations but also that the deep cerebellar nuclei may also play a similar role. Thus, we analysed local field potentials and single-unit activities in the deep cerebellar nuclei before, during and after electric stimulation in the inferior olive of awake mice. A high-frequency oscillation of 350 Hz triggered by the stimulation of the inferior olive, within the beta-gamma range, was observed in the deep cerebellar nuclei. The amplitude and frequency of the oscillation were independent of the frequency of stimulation. This oscillation emerged during the period of stimulation and persisted after the end of the stimulation. The oscillation coincided with the inhibition of deep cerebellar neurons. As the inhibition of the deep cerebellar nuclei is related to inhibitory inputs from Purkinje cells, we speculate that the oscillation represents the unmasking of the synchronous activation of another subtype of deep cerebellar neuronal subtype, devoid of GABA receptors and under the direct control of the climbing fibres from the inferior olive. Still, the mechanism sustaining this oscillation remains to be deciphered. Our study sheds new light on the role of the olivo-cerebellar loop as the final output control of the intercerebellar circuitry.
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Affiliation(s)
- Julian Cheron
- Laboratory of Electrophysiology, Université de Mons, Mons, Belgium.,Laboratory of Neurophysiology and Movement Biomechanics, Neuroscience Institute, Université Libre de Bruxelles, Route de Lennik 808, Brussels, 1070, Belgium
| | - Guy Cheron
- Laboratory of Electrophysiology, Université de Mons, Mons, Belgium.,Laboratory of Neurophysiology and Movement Biomechanics, Neuroscience Institute, Université Libre de Bruxelles, Route de Lennik 808, Brussels, 1070, Belgium
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Garden DLF, Oostland M, Jelitai M, Rinaldi A, Duguid I, Nolan MF. Inferior Olive HCN1 Channels Coordinate Synaptic Integration and Complex Spike Timing. Cell Rep 2018; 22:1722-1733. [PMID: 29444426 PMCID: PMC5847187 DOI: 10.1016/j.celrep.2018.01.069] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 01/03/2018] [Accepted: 01/22/2018] [Indexed: 02/07/2023] Open
Abstract
Cerebellar climbing-fiber-mediated complex spikes originate from neurons in the inferior olive (IO), are critical for motor coordination, and are central to theories of cerebellar learning. Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels expressed by IO neurons have been considered as pacemaker currents important for oscillatory and resonant dynamics. Here, we demonstrate that in vitro, network actions of HCN1 channels enable bidirectional glutamatergic synaptic responses, while local actions of HCN1 channels determine the timing and waveform of synaptically driven action potentials. These roles are distinct from, and may complement, proposed pacemaker functions of HCN channels. We find that in behaving animals HCN1 channels reduce variability in the timing of cerebellar complex spikes, which serve as a readout of IO spiking. Our results suggest that spatially distributed actions of HCN1 channels enable the IO to implement network-wide rules for synaptic integration that modulate the timing of cerebellar climbing fiber signals. HCN1 channels in IO neurons control synaptic response and spiking activity Network actions of HCN1 channels enable bidirectional synaptic responses Local actions of HCN1 channels control spike timing and spikelet number In awake mice, HCN1 channels reduce timing variability of cerebellar complex spikes
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Affiliation(s)
- Derek L F Garden
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Marlies Oostland
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Marta Jelitai
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Arianna Rinaldi
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Ian Duguid
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Matthew F Nolan
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh EH8 9XD, UK.
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Membrane potential synchrony of neurons in anterior cingulate cortex plays a pivotal role in generation of neuropathic pain. Sci Rep 2018; 8:1691. [PMID: 29374274 PMCID: PMC5785961 DOI: 10.1038/s41598-018-20080-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 01/09/2018] [Indexed: 12/22/2022] Open
Abstract
The pathophysiology of neuropathic pain generation has not been fully investigated. Previous studies have primarily focused on changes in the properties of single neurons in the brain after nerve injury; however, little is known concerning the role of neuron-to-neuron connections in neuropathic pain pathogenesis. Synaptic transmission potentiation in anterior cingulate cortex (ACC) has been confirmed to be responsible for the formation of neuropathic pain. Thus, analysis of interneuronal connections in the ACC is an important approach for understanding the mechanism of neuropathic pain since it provides information on the potency of synaptic transmission. Here, we recorded membrane potentials from pairs of ACC neurons in anaesthetised rats and found that cross-correlations between pairs of ACC neurons significantly increased after surgery for chronic constriction injury (CCI). Moreover, CCI surgery could also enhance the power spectrum density of lower and higher-frequency membrane oscillations while having no effect on middle-frequency oscillations. The activation of membrane potential synchrony and power spectrum was reversed by the electrical synapse blocker mefloquine and pain behaviour was simultaneously alleviated. Our results may indicate that activation of membrane potential synchrony contributes to generation of neuropathic pain.
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Nagy JI, Pereda AE, Rash JE. Electrical synapses in mammalian CNS: Past eras, present focus and future directions. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2018; 1860:102-123. [PMID: 28577972 PMCID: PMC5705454 DOI: 10.1016/j.bbamem.2017.05.019] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 05/26/2017] [Accepted: 05/27/2017] [Indexed: 12/19/2022]
Abstract
Gap junctions provide the basis for electrical synapses between neurons. Early studies in well-defined circuits in lower vertebrates laid the foundation for understanding various properties conferred by electrical synaptic transmission. Knowledge surrounding electrical synapses in mammalian systems unfolded first with evidence indicating the presence of gap junctions between neurons in various brain regions, but with little appreciation of their functional roles. Beginning at about the turn of this century, new approaches were applied to scrutinize electrical synapses, revealing the prevalence of neuronal gap junctions, the connexin protein composition of many of those junctions, and the myriad diverse neural systems in which they occur in the mammalian CNS. Subsequent progress indicated that electrical synapses constitute key elements in synaptic circuitry, govern the collective activity of ensembles of electrically coupled neurons, and in part orchestrate the synchronized neuronal network activity and rhythmic oscillations that underlie fundamental integrative processes. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- James I Nagy
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, Manitoba, Canada.
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, 10461, United States
| | - John E Rash
- Department of Biomedical Sciences, and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, CO 80523, United States
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Bazzigaluppi P, Isenia SC, Haasdijk ED, Elgersma Y, De Zeeuw CI, van der Giessen RS, de Jeu MTG. Modulation of Murine Olivary Connexin 36 Gap Junctions by PKA and CaMKII. Front Cell Neurosci 2017; 11:397. [PMID: 29311830 PMCID: PMC5735106 DOI: 10.3389/fncel.2017.00397] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 11/28/2017] [Indexed: 11/15/2022] Open
Abstract
The inferior olive (IO) is a nucleus located in the brainstem and it is part of the olivo-cerebellar loop. This circuit plays a fundamental role in generation and acquisition of coherent motor patterns and it relies on synchronous activation of groups of Purkinje cells (PC) in the cerebellar cortex. IO neurons integrate their intrinsic oscillatory activity with excitatory inputs coming from the somatosensory system and inhibitory feedback coming from the cerebellar nuclei. Alongside these chemical synaptic inputs, IO neurons are coupled to one another via connexin 36 (Cx36) containing gap junctions (GJs) that create a functional syncytium between neurons. Communication between olivary neurons is regulated by these GJs and their correct functioning contributes to coherent oscillations in the IO and proper motor learning. Here, we explore the cellular pathways that can regulate the coupling between olivary neurons. We combined in vitro electrophysiology and immunohistochemistry (IHC) on mouse acute brain slices to unravel the pathways that regulate olivary coupling. We found that enhancing the activity of the protein kinase A (PKA) pathway and blocking the Ca2+/calmodulin-dependent protein kinase II (CaMKII) pathway can both down-regulate the size of the coupled network. However, these two kinases follow different mechanisms of action. Our results suggest that activation of the PKA pathway reduces the opening probability of the Cx36 GJs, whereas inhibition of the CaMKII pathway reduces the number of Cx36 GJs. The low densities of Cx36 proteins and electrical synapses in βCaMKII knock-out mice point towards an essential role for this protein kinase in regulating the density of GJs in the IO. Thus, the level of olivary coupling is a dynamic process and regulated by a variety of enzymes modulating GJs expression, docking and activity.
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Affiliation(s)
- Paolo Bazzigaluppi
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, Netherlands
| | - Sheena C Isenia
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, Netherlands
| | - Elize D Haasdijk
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, Netherlands
| | - Ype Elgersma
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, Netherlands
| | - Chris I De Zeeuw
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, Netherlands
| | | | - Marcel T G de Jeu
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, Netherlands
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42
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Leybaert L, Lampe PD, Dhein S, Kwak BR, Ferdinandy P, Beyer EC, Laird DW, Naus CC, Green CR, Schulz R. Connexins in Cardiovascular and Neurovascular Health and Disease: Pharmacological Implications. Pharmacol Rev 2017; 69:396-478. [PMID: 28931622 PMCID: PMC5612248 DOI: 10.1124/pr.115.012062] [Citation(s) in RCA: 179] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Connexins are ubiquitous channel forming proteins that assemble as plasma membrane hemichannels and as intercellular gap junction channels that directly connect cells. In the heart, gap junction channels electrically connect myocytes and specialized conductive tissues to coordinate the atrial and ventricular contraction/relaxation cycles and pump function. In blood vessels, these channels facilitate long-distance endothelial cell communication, synchronize smooth muscle cell contraction, and support endothelial-smooth muscle cell communication. In the central nervous system they form cellular syncytia and coordinate neural function. Gap junction channels are normally open and hemichannels are normally closed, but pathologic conditions may restrict gap junction communication and promote hemichannel opening, thereby disturbing a delicate cellular communication balance. Until recently, most connexin-targeting agents exhibited little specificity and several off-target effects. Recent work with peptide-based approaches has demonstrated improved specificity and opened avenues for a more rational approach toward independently modulating the function of gap junctions and hemichannels. We here review the role of connexins and their channels in cardiovascular and neurovascular health and disease, focusing on crucial regulatory aspects and identification of potential targets to modify their function. We conclude that peptide-based investigations have raised several new opportunities for interfering with connexins and their channels that may soon allow preservation of gap junction communication, inhibition of hemichannel opening, and mitigation of inflammatory signaling.
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Affiliation(s)
- Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Paul D Lampe
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Stefan Dhein
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Brenda R Kwak
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Peter Ferdinandy
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Eric C Beyer
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Dale W Laird
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Christian C Naus
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Colin R Green
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Rainer Schulz
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
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Coulon P, Landisman CE. The Potential Role of Gap Junctional Plasticity in the Regulation of State. Neuron 2017; 93:1275-1295. [PMID: 28334604 DOI: 10.1016/j.neuron.2017.02.041] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 01/20/2017] [Accepted: 02/22/2017] [Indexed: 11/19/2022]
Abstract
Electrical synapses are the functional correlate of gap junctions and allow transmission of small molecules and electrical current between coupled neurons. Instead of static pores, electrical synapses are actually plastic, similar to chemical synapses. In the thalamocortical system, gap junctions couple inhibitory neurons that are similar in their biochemical profile, morphology, and electrophysiological properties. We postulate that electrical synaptic plasticity among inhibitory neurons directly interacts with the switching between different firing patterns in a state-dependent and type-dependent manner. In neuronal networks, electrical synapses may function as a modifiable resonance feedback system that enables stable oscillations. Furthermore, the plasticity of electrical synapses may play an important role in regulation of state, synchrony, and rhythmogenesis in the mammalian thalamocortical system, similar to chemical synaptic plasticity. Based on their plasticity, rich diversity, and specificity, electrical synapses are thus likely to participate in the control of consciousness and attention.
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Affiliation(s)
- Philippe Coulon
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA 98101, USA.
| | - Carole E Landisman
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA 98101, USA.
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Nagy JI, Rash JE. Cx36, Cx43 and Cx45 in mouse and rat cerebellar cortex: species-specific expression, compensation in Cx36 null mice and co-localization in neurons vs. glia. Eur J Neurosci 2017; 46:1790-1804. [PMID: 28561933 DOI: 10.1111/ejn.13614] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/13/2017] [Accepted: 05/24/2017] [Indexed: 12/13/2022]
Abstract
Electrical synapses formed by connexin36 (Cx36)-containing gap junctions between interneurons in the cerebellar cortex have been well characterized, including those formed between basket cells and between Golgi cells, and there is gene reporter-based evidence for the expression of connexin45 (Cx45) in the cerebellar molecular layer. Here, we used immunofluorescence approaches to further investigate expression patterns of Cx36 and Cx45 in this layer and to examine localization relationships of these connexins with each other and with glial connexin43 (Cx43). In mice, strain differences were found, such that punctate labelling for Cx36 was differentially distributed in the molecular layer of C57BL/6 vs. CD1 mice. In mice with EGFP reporter representing Cx36 expression, Cx36-puncta were localized to processes of stellate cells and other cerebellar interneurons. Punctate labelling of Cx45 was faint in the molecular layer of wild-type mice and was increased in intensity in mice with Cx36 gene ablation. The vast majority of Cx36-puncta co-localized with Cx45-puncta, which in turn was associated with the scaffolding protein zonula occludens-1. In rats, Cx45-puncta were also co-localized with Cx36-puncta and additionally occurred along Bergmann glial processes adjacent to Cx43-puncta. The results indicate strain and species differences in Cx36 as well as Cx45 expression, possible compensatory processes after loss of Cx36 expression and localization of Cx45 to both neuronal and Bergmann glial gap junctions. Further, expression of both Cx43 and Cx45 in Bergmann glia of rat may contribute to the complex properties of junctional coupling between these cells and perhaps to their reported coupling with Purkinje cells.
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Affiliation(s)
- J I Nagy
- Department of Physiology and Pathophysiology, Faculty of Medicine, University of Manitoba, 745 Bannatyne Ave, Winnipeg, MB, R3E 0J9, Canada
| | - J E Rash
- Department of Biomedical Sciences, and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, CO, USA
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45
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Sevetson J, Fittro S, Heckman E, Haas JS. A calcium-dependent pathway underlies activity-dependent plasticity of electrical synapses in the thalamic reticular nucleus. J Physiol 2017; 595:4417-4430. [PMID: 28369952 DOI: 10.1113/jp274049] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 03/14/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Electrical synapses are modified by various forms of activity, including paired activity in coupled neurons and tetanization of the input to coupled neurons. We show that plasticity of electrical synapses that results from paired spiking activity in coupled neurons depends on calcium influx and calcium-initiated signalling pathways. Plasticity that results from tetanization of input fibres does not depend on calcium influx or dynamics. These results imply that electrically coupled neurons have distinct sets of mechanisms for adjusting coupling according to the specific type of activity they experience. ABSTRACT Recent results have demonstrated modification of electrical synapse strength by varied forms of neuronal activity. However, the mechanisms underlying plasticity induction in central mammalian neurons are unclear. Here we show that the two established inductors of plasticity at electrical synapses in the thalamic reticular nucleus - paired burst spiking in coupled neurons, and mGluR-dependent tetanization of synaptic input - are separate pathways that converge at a common downstream endpoint. Using occlusion experiments and pharmacology in patched pairs of coupled neurons in vitro, we show that burst-induced depression depends on calcium entry via voltage-gated channels, is blocked by BAPTA chelation, and recruits intracellular calcium release on its way to activation of phosphatase activity. In contrast, mGluR-dependent plasticity is independent of calcium entry or calcium dynamics. Together, these results show that the spiking-initiated mechanisms underlying electrical synapse plasticity are similar to those that induce plasticity at chemical synapses, and offer the possibility that calcium-regulated mechanisms may also lead to alternate outcomes, such as potentiation. Because these mechanistic elements are widely found in mature neurons, we expect them to apply broadly to electrical synapses across the brain, acting as the crucial link between neuronal activity and electrical synapse strength.
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Affiliation(s)
- Jessica Sevetson
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA, 18015, USA
| | - Sarah Fittro
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA, 18015, USA
| | - Emily Heckman
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA, 18015, USA
| | - Julie S Haas
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA, 18015, USA
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46
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Connors BW. Synchrony and so much more: Diverse roles for electrical synapses in neural circuits. Dev Neurobiol 2017; 77:610-624. [PMID: 28245529 DOI: 10.1002/dneu.22493] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 02/05/2017] [Accepted: 02/14/2017] [Indexed: 11/09/2022]
Abstract
Electrical synapses are neuronal gap junctions that are ubiquitous across brain regions and species. The biophysical properties of most electrical synapses are relatively simple-transcellular channels allow nearly ohmic, bidirectional flow of ionic current. Yet these connections can play remarkably diverse roles in different neural circuit contexts. Recent findings illustrate how electrical synapses may excite or inhibit, synchronize or desynchronize, augment or diminish rhythms, phase-shift, detect coincidences, enhance signals relative to noise, adapt, and interact with nonlinear membrane and transmitter-release mechanisms. Most of these functions are likely to be widespread in central nervous systems. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 610-624, 2017.
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Affiliation(s)
- Barry W Connors
- Department of Neuroscience, Brown University, Providence, Rhode Island
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47
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Belousov AB, Fontes JD, Freitas-Andrade M, Naus CC. Gap junctions and hemichannels: communicating cell death in neurodevelopment and disease. BMC Cell Biol 2017; 18:4. [PMID: 28124625 PMCID: PMC5267333 DOI: 10.1186/s12860-016-0120-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Gap junctions are unique membrane channels that play a significant role in intercellular communication in the developing and mature central nervous system (CNS). These channels are composed of connexin proteins that oligomerize into hexamers to form connexons or hemichannels. Many different connexins are expressed in the CNS, with some specificity with regard to the cell types in which distinct connexins are found, as well as the timepoints when they are expressed in the developing and mature CNS. Both the main neuronal Cx36 and glial Cx43 play critical roles in neurodevelopment. These connexins also mediate distinct aspects of the CNS response to pathological conditions. An imbalance in the expression, translation, trafficking and turnover of connexins, as well as mutations of connexins, can impact their function in the context of cell death in neurodevelopment and disease. With the ever-increasing understanding of connexins in the brain, therapeutic strategies could be developed to target these membrane channels in various neurological disorders.
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Affiliation(s)
- Andrei B Belousov
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, The University of Kansas, Kansas City, KS, 66160, USA
| | - Joseph D Fontes
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, The University of Kansas, Kansas City, KS, 66160, USA
| | - Moises Freitas-Andrade
- Department of Cellular & Physiological Sciences, Faculty of Medicine, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Christian C Naus
- Department of Cellular & Physiological Sciences, Faculty of Medicine, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada.
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48
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Garden DLF, Rinaldi A, Nolan MF. Active integration of glutamatergic input to the inferior olive generates bidirectional postsynaptic potentials. J Physiol 2016; 595:1239-1251. [PMID: 27767209 PMCID: PMC5309349 DOI: 10.1113/jp273424] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 10/14/2016] [Indexed: 11/15/2022] Open
Abstract
Key points We establish experimental preparations for optogenetic investigation of glutamatergic input to the inferior olive. Neurones in the principal olivary nucleus receive monosynaptic extra‐somatic glutamatergic input from the neocortex. Glutamatergic inputs to neurones in the inferior olive generate bidirectional postsynaptic potentials (PSPs), with a fast excitatory component followed by a slower inhibitory component. Small conductance calcium‐activated potassium (SK) channels are required for the slow inhibitory component of glutamatergic PSPs and oppose temporal summation of inputs at intervals ≤ 20 ms. Active integration of synaptic input within the inferior olive may play a central role in control of olivo‐cerebellar climbing fibre signals.
Abstract The inferior olive plays a critical role in motor coordination and learning by integrating diverse afferent signals to generate climbing fibre inputs to the cerebellar cortex. While it is well established that climbing fibre signals are important for motor coordination, the mechanisms by which neurones in the inferior olive integrate synaptic inputs and the roles of particular ion channels are unclear. Here, we test the hypothesis that neurones in the inferior olive actively integrate glutamatergic synaptic inputs. We demonstrate that optogenetically activated long‐range synaptic inputs to the inferior olive, including projections from the motor cortex, generate rapid excitatory potentials followed by slower inhibitory potentials. Synaptic projections from the motor cortex preferentially target the principal olivary nucleus. We show that inhibitory and excitatory components of the bidirectional synaptic potentials are dependent upon AMPA (GluA) receptors, are GABAA independent, and originate from the same presynaptic axons. Consistent with models that predict active integration of synaptic inputs by inferior olive neurones, we find that the inhibitory component is reduced by blocking large conductance calcium‐activated potassium channels with iberiotoxin, and is abolished by blocking small conductance calcium‐activated potassium channels with apamin. Summation of excitatory components of synaptic responses to inputs at intervals ≤ 20 ms is increased by apamin, suggesting a role for the inhibitory component of glutamatergic responses in temporal integration. Our results indicate that neurones in the inferior olive implement novel rules for synaptic integration and suggest new principles for the contribution of inferior olive neurones to coordinated motor behaviours. We establish experimental preparations for optogenetic investigation of glutamatergic input to the inferior olive. Neurones in the principal olivary nucleus receive monosynaptic extra‐somatic glutamatergic input from the neocortex. Glutamatergic inputs to neurones in the inferior olive generate bidirectional postsynaptic potentials (PSPs), with a fast excitatory component followed by a slower inhibitory component. Small conductance calcium‐activated potassium (SK) channels are required for the slow inhibitory component of glutamatergic PSPs and oppose temporal summation of inputs at intervals ≤ 20 ms. Active integration of synaptic input within the inferior olive may play a central role in control of olivo‐cerebellar climbing fibre signals.
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Affiliation(s)
- Derek L F Garden
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Arianna Rinaldi
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Matthew F Nolan
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, EH8 9XD, UK
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Eriksson D. Estimating Neural Background Input with Controlled and Fast Perturbations: A Bandwidth Comparison between Inhibitory Opsins and Neural Circuits. Front Neural Circuits 2016; 10:58. [PMID: 27574506 PMCID: PMC4983554 DOI: 10.3389/fncir.2016.00058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Accepted: 07/25/2016] [Indexed: 11/13/2022] Open
Abstract
To test the importance of a certain cell type or brain area it is common to make a "lack of function" experiment in which the neuronal population of interest is inhibited. Here we review physiological and methodological constraints for making controlled perturbations using the corticothalamic circuit as an example. The brain with its many types of cells and rich interconnectivity offers many paths through which a perturbation can spread within a short time. To understand the side effects of the perturbation one should record from those paths. We find that ephaptic effects, gap-junctions, and fast chemical synapses are so fast that they can react to the perturbation during the few milliseconds it takes for an opsin to change the membrane potential. The slow chemical synapses, astrocytes, extracellular ions and vascular signals, will continue to give their physiological input for around 20 ms before they also react to the perturbation. Although we show that some pathways can react within milliseconds the strength/speed reported in this review should be seen as an upper bound since we have omitted how polysynaptic signals are attenuated. Thus the number of additional recordings that has to be made to control for the perturbation side effects is expected to be fewer than proposed here. To summarize, the reviewed literature not only suggests that it is possible to make controlled "lack of function" experiments, but, it also suggests that such a "lack of function" experiment can be used to measure the context of local neural computations.
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Affiliation(s)
- David Eriksson
- Center for Neuroscience, Albert Ludwig University of FreiburgFreiburg, Germany; BrainLinks-BrainTools, Albert Ludwig University of FreiburgFreiburg, Germany
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50
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Bazzigaluppi P, de Jeu MTG. Heterogeneous Expression of T-type Ca(2+) Channels Defines Different Neuronal Populations in the Inferior Olive of the Mouse. Front Cell Neurosci 2016; 10:192. [PMID: 27540355 PMCID: PMC4972830 DOI: 10.3389/fncel.2016.00192] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 07/19/2016] [Indexed: 11/17/2022] Open
Abstract
The neurons in the inferior olive express subthreshold oscillations in their membrane potential. This oscillatory activity is known to drive synchronous activity in the cerebellar cortex and plays a role in motor learning and motor timing. In the past years, it was commonly thought that olivary neurons belonged to a unique population of oscillating units and that oscillation properties were exclusively dependent on network settings and/or synaptic inputs. The origin of olivary oscillations is now known to be a local phenomenon and is generated by a combination of conductances. In the present work, we show the existence of at least two neuronal populations that can be distinguished on the basis of the presence or absence of low-voltage activated Ca2+ channels. The expression of this channel determines the oscillatory behavior of olivary neurons. Furthermore, the number of cells that express this channel is different between sub nuclei of the inferior olive. These findings clearly indicate the functional variability within and between olivary sub nuclei.
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Affiliation(s)
- Paolo Bazzigaluppi
- Department of Neuroscience, Erasmus Medical Center Rotterdam, Netherlands
| | - Marcel T G de Jeu
- Department of Neuroscience, Erasmus Medical Center Rotterdam, Netherlands
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