1
|
Snyder RR, Blitz DM. Multiple intrinsic membrane properties are modulated in a switch from single- to dual-network activity. J Neurophysiol 2022; 128:1181-1198. [PMID: 36197020 PMCID: PMC9621714 DOI: 10.1152/jn.00337.2022] [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: 08/03/2022] [Revised: 09/14/2022] [Accepted: 10/01/2022] [Indexed: 11/22/2022] Open
Abstract
Neural network flexibility includes changes in neuronal participation between networks, such as the switching of neurons between single- and dual-network activity. We previously identified a neuron that is recruited to burst in time with an additional network via modulation of its intrinsic membrane properties, instead of being recruited synaptically into the second network. However, the modulated intrinsic properties were not determined. Here, we use small networks in the Jonah crab (Cancer borealis) stomatogastric nervous system (STNS) to examine modulation of intrinsic properties underlying neuropeptide (Gly1-SIFamide)-elicited neuronal switching. The lateral posterior gastric neuron (LPG) switches from exclusive participation in the fast pyloric (∼1 Hz) network, due to electrical coupling, to dual-network activity that includes periodic escapes from the fast rhythm via intrinsically generated oscillations at the slower gastric mill network frequency (∼0.1 Hz). We isolated LPG from both networks by pharmacology and hyperpolarizing current injection. Gly1-SIFamide increased LPG intrinsic excitability and rebound from inhibition and decreased spike frequency adaptation, which can all contribute to intrinsic bursting. Using ion substitution and channel blockers, we found that a hyperpolarization-activated current, a persistent sodium current, and calcium or calcium-related current(s) appear to be primary contributors to Gly1-SIFamide-elicited LPG intrinsic bursting. However, this intrinsic bursting was more sensitive to blocking currents when LPG received rhythmic electrical coupling input from the fast network than in the isolated condition. Overall, a switch from single- to dual-network activity can involve modulation of multiple intrinsic properties, while synaptic input from a second network can shape the contributions of these properties.NEW & NOTEWORTHY Neuropeptide-elicited intrinsic bursting was recently determined to switch a neuron from single- to dual-network participation. Here we identified multiple intrinsic properties modulated in the dual-network state and candidate ion channels underlying the intrinsic bursting. Bursting at the second network frequency was more sensitive to blocking currents in the dual-network state than when neurons were synaptically isolated from their home network. Thus, synaptic input can shape the contributions of modulated intrinsic properties underlying dual-network activity.
Collapse
Affiliation(s)
- Ryan R Snyder
- Department of Biology and Center for Neuroscience, Miami University, Oxford, Ohio
| | - Dawn M Blitz
- Department of Biology and Center for Neuroscience, Miami University, Oxford, Ohio
| |
Collapse
|
2
|
Wang H, Haas JS. GABA BR Modulation of Electrical Synapses and Plasticity in the Thalamic Reticular Nucleus. Int J Mol Sci 2021; 22:ijms222212138. [PMID: 34830020 PMCID: PMC8621091 DOI: 10.3390/ijms222212138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 10/31/2021] [Accepted: 11/05/2021] [Indexed: 11/16/2022] Open
Abstract
Two distinct types of neuronal activity result in long-term depression (LTD) of electrical synapses, with overlapping biochemical intracellular signaling pathways that link activity to synaptic strength, in electrically coupled neurons of the thalamic reticular nucleus (TRN). Because components of both signaling pathways can also be modulated by GABAB receptor activity, here we examined the impact of GABAB receptor activation on the two established inductors of LTD in electrical synapses. Recording from patched pairs of coupled rat neurons in vitro, we show that GABAB receptor inactivation itself induces a modest depression of electrical synapses and occludes LTD induction by either paired bursting or metabotropic glutamate receptor (mGluR) activation. GABAB activation also occludes LTD from either paired bursting or mGluR activation. Together, these results indicate that afferent sources of GABA, such as those from the forebrain or substantia nigra to the reticular nucleus, gate the induction of LTD from either neuronal activity or afferent glutamatergic receptor activation. These results add to a growing body of evidence that the regulation of thalamocortical transmission and sensory attention by TRN is modulated and controlled by other brain regions. Significance: We show that electrical synapse plasticity is gated by GABAB receptors in the thalamic reticular nucleus. This effect is a novel way for afferent GABAergic input from the basal ganglia to modulate thalamocortical relay and is a possible mediator of intra-TRN inhibitory effects.
Collapse
|
3
|
Neuronal Switching between Single- and Dual-Network Activity via Modulation of Intrinsic Membrane Properties. J Neurosci 2021; 41:7848-7863. [PMID: 34349000 DOI: 10.1523/jneurosci.0286-21.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 07/26/2021] [Accepted: 07/28/2021] [Indexed: 11/21/2022] Open
Abstract
Oscillatory networks underlie rhythmic behaviors (e.g., walking, chewing) and complex behaviors (e.g., memory formation, decision-making). Flexibility of oscillatory networks includes neurons switching between single- and dual-network participation, even generating oscillations at two distinct frequencies. Modulation of synaptic strength can underlie this neuronal switching. Here we ask whether switching into dual-frequency oscillations can also result from modulation of intrinsic neuronal properties. The isolated stomatogastric nervous system of male Cancer borealis crabs contains two well-characterized rhythmic feeding-related networks (pyloric, ∼1 Hz; gastric mill, ∼0.1 Hz). The identified modulatory projection neuron MCN5 causes the pyloric-only lateral posterior gastric (LPG) neuron to switch to dual pyloric/gastric mill bursting. Bath applying the MCN5 neuropeptide transmitter Gly1-SIFamide only partly mimics the LPG switch to dual activity because of continued LP neuron inhibition of LPG. Here, we find that MCN5 uses a cotransmitter, glutamate, to inhibit LP, unlike Gly1-SIFamide excitation of LP. Thus, we modeled the MCN5-elicited LPG switching with Gly1-SIFamide application and LP photoinactivation. Using hyperpolarization of pyloric pacemaker neurons and gastric mill network neurons, we found that LPG pyloric-timed oscillations require rhythmic electrical synaptic input. However, LPG gastric mill-timed oscillations do not require any pyloric/gastric mill synaptic input and are voltage-dependent. Thus, we identify modulation of intrinsic properties as an additional mechanism for switching a neuron into dual-frequency activity. Instead of synaptic modulation switching a neuron into a second network as a passive follower, modulation of intrinsic properties could enable a switching neuron to become an active contributor to rhythm generation in the second network.SIGNIFICANCE STATEMENT Neuromodulation of oscillatory networks can enable network neurons to switch from single- to dual-network participation, even when two networks oscillate at distinct frequencies. We used small, well-characterized networks to determine whether modulation of synaptic strength, an identified mechanism for switching, is necessary for dual-network recruitment. We demonstrate that rhythmic electrical synaptic input is required for continued linkage with a "home" network, whereas modulation of intrinsic properties enables a neuron to generate oscillations at a second frequency. Neuromodulator-induced switches in neuronal participation between networks occur in motor, cognitive, and sensory networks. Our study highlights the importance of considering intrinsic properties as a pivotal target for enabling parallel participation of a neuron in two oscillatory networks.
Collapse
|
4
|
Mushtaq M, Haq RU, Anwar W, Marshall L, Bazhenov M, Zia K, Alam H, Hertel L, Awan AA, Martinetz T. A computational study of suppression of sharp wave ripple complexes by controlling calcium and gap junctions in pyramidal cells. Bioengineered 2021; 12:2603-2615. [PMID: 34115572 PMCID: PMC8806748 DOI: 10.1080/21655979.2021.1936894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hippocampus plays a key role in memory formation and learning. According to the concept of active systems memory consolidation, transiently stored memory traces are transferred from the hippocampus into the neocortex for permanent storage. This phenomenon relies on hippocampal network oscillations, particularly sharp wave ripples [SPW-Rs). In this process prior saved data in the hippocampus may be reactivated. Recent investigations reveal that several neurotransmitters and neuromodulators including norepinephrine, acetylcholine, serotonin, etc., suppress SPW-Rs activity in rodents’ hippocampal slices. This suppression of SPW-Rs may depend on various presynaptic and postsynaptic parameters including decrease in calcium influx, hyperpolarization/depolarization and alteration in gap junctions’ function in pyramidal cells. In this study, we demonstrate the impact of calcium influx and gap junctions on pyramidal cells for the modulation of SPW-Rs in a computational model of CA1. We used,SPW-Rs model with some modifications. SPW-Rs are simulated with gradual reduction of calcium and with decreasing conductance through gap junctions in PCs. Both, with calcium reduction as well as with conductance reduction through gap junctions, SPW-Rs are suppressed. Both effects add up synergistically in combination.
Collapse
Affiliation(s)
- Muhammad Mushtaq
- Institute for Neuro- and Bioinformatics, University of Lübeck, Lübeck, Germany
| | - Rizwan Ul Haq
- Department of Pharmaceutical Sciences, Abbottabad University of Science & Technology, Abbottabad, Pakistan
| | - Waqas Anwar
- Department of Information Technologies, Comsats University, Lahore Campus, Pakistan
| | - Lisa Marshall
- Institute of Experimental and Clinical Pharmacology, University of Lübeck, Lübeck, Germany
| | - Maxim Bazhenov
- Department of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Kashif Zia
- Faculty of Computing and Information Technology, Sohar University, Al Sohar, Oman
| | - Hina Alam
- Pakistan Institute of Medical Sciences, Islamabad, Pakistan
| | - Lars Hertel
- Institute for Neuro- and Bioinformatics, University of Lübeck, Lübeck, Germany
| | - Abdul Aleem Awan
- Department of Pharmaceutical Sciences, Abbottabad University of Science & Technology, Abbottabad, Pakistan
| | - Thomas Martinetz
- Institute for Neuro- and Bioinformatics, University of Lübeck, Lübeck, Germany
| |
Collapse
|
5
|
Zhang Y, Liu C, Zhang L, Zhou W, Yu S, Yi R, Luo D, Fu X. Effects of Propofol on Electrical Synaptic Strength in Coupling Reticular Thalamic GABAergic Parvalbumin-Expressing Neurons. Front Neurosci 2020; 14:364. [PMID: 32410945 PMCID: PMC7198707 DOI: 10.3389/fnins.2020.00364] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 03/25/2020] [Indexed: 12/17/2022] Open
Abstract
Electrical synapses between neurons exhibit a high degree of plasticity, which makes critical contributions to neuronal communication. The GABAergic parvalbumin-expressing (PV+) neurons in the thalamic reticular nucleus (TRN) interact with each other through electrical and chemical synapses. Plasticity of electrical synaptic transmission in TRN plays a key role in regulating thalamocortical and corticothalamic circuits and even the formation of consciousness. We here examined the effects of propofol, a commonly used general anesthetic agent, on the strength of electrical synapses between TRN PV+ neurons by fluorescence-guided patch-clamp recording and pharmacological methods. Results show that 100 μM propofol reduced the electrical synaptic strength between TRN PV+ neurons. Notably, the propofol-induced depression of electrical synaptic strength between TRN PV+ neurons was diminished by saclofen (10 μM, antagonist of GABAB receptors), but not blocked by gabazine (10 μM, antagonist of GABAA receptors). Application of baclofen (10 μM, agonist of GABAB receptors), similar to propofol, also reduced the electrical synaptic strength between TRN PV+ neurons. Moreover, the propofol-induced depression of electrical synaptic strength between TRN PV+ neurons was abolished by 9-CPA (100 μM, specific adenylyl cyclase inhibitor), and by KT5720 (1 μM, selective inhibitor of PKA). Our findings indicate that propofol acts on metabotropic GABAB receptors, resulting in a depression of electrical synaptic transmission of coupled TRN PV+ neurons, which is mediated by the adenylyl cyclase-cAMP-PKA signaling pathway. Our findings also imply that propofol may change the thalamocortical communication via inducing depression of electrical synaptic strength in the TRN.
Collapse
Affiliation(s)
- Yu Zhang
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical University, Guizhou, China.,Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Chengxi Liu
- Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Guizhou, China
| | - Lin Zhang
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Wenjing Zhou
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Shouyang Yu
- Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Guizhou, China
| | - Rulan Yi
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Dan Luo
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Guizhou, China
| | - Xiaoyun Fu
- Department of Critical Care Medicine, Affiliated Hospital of Zunyi Medical University, Guizhou, China
| |
Collapse
|
6
|
Sotelo C. The History of the Synapse. Anat Rec (Hoboken) 2020; 303:1252-1279. [DOI: 10.1002/ar.24392] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 09/27/2019] [Indexed: 11/12/2022]
Affiliation(s)
- Constantino Sotelo
- Sorbonne Université, INSERM, CNRS, Institut de la Vision Paris France
- Instituto de Neurociencias, Consejo Superior de Investigaciones Científicas (CSIC)‐Universidad Miguel Hernández (UMH) San Juan de Alicante Spain
| |
Collapse
|
7
|
Connexins-Based Hemichannels/Channels and Their Relationship with Inflammation, Seizures and Epilepsy. Int J Mol Sci 2019; 20:ijms20235976. [PMID: 31783599 PMCID: PMC6929063 DOI: 10.3390/ijms20235976] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 11/13/2019] [Accepted: 11/20/2019] [Indexed: 12/11/2022] Open
Abstract
Connexins (Cxs) are a family of 21 protein isoforms, eleven of which are expressed in the central nervous system, and they are found in neurons and glia. Cxs form hemichannels (connexons) and channels (gap junctions/electric synapses) that permit functional and metabolic coupling between neurons and astrocytes. Altered Cx expression and function is involved in inflammation and neurological diseases. Cxs-based hemichannels and channels have a relevance to seizures and epilepsy in two ways: First, this pathological condition increases the opening probability of hemichannels in glial cells to enable gliotransmitter release, sustaining the inflammatory process and exacerbating seizure generation and epileptogenesis, and second, the opening of channels favors excitability and synchronization through coupled neurons. These biological events highlight the global pathological mechanism of epilepsy, and the therapeutic potential of Cxs-based hemichannels and channels. Therefore, this review describes the role of Cxs in neuroinflammation and epilepsy and examines how the blocking of channels and hemichannels may be therapeutic targets of anti-convulsive and anti-epileptic treatments.
Collapse
|
8
|
Alcamí P, Pereda AE. Beyond plasticity: the dynamic impact of electrical synapses on neural circuits. Nat Rev Neurosci 2019; 20:253-271. [DOI: 10.1038/s41583-019-0133-5] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
|
9
|
Traub RD, Whittington MA, Gutiérrez R, Draguhn A. Electrical coupling between hippocampal neurons: contrasting roles of principal cell gap junctions and interneuron gap junctions. Cell Tissue Res 2018; 373:671-691. [PMID: 30112572 DOI: 10.1007/s00441-018-2881-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 07/03/2018] [Indexed: 11/28/2022]
Abstract
There is considerable experimental evidence, anatomical and physiological, that gap junctions exist in the hippocampus. Electrical coupling through these gap junctions may be divided into three types: between principal neurons, between interneurons and at mixed chemical (glutamatergic)/electrical synapses. An approach, combining in vitro experimental with modeling techniques, sheds some light on the functional consequences of electrical coupling, for network oscillations and for seizures. Additionally, in vivo experiments, using mouse connexin knockouts, suggest that the presence of electrical coupling is important for optimal performance on selected behavioral tasks; however, the interpretation of such data, in cellular terms, has so far proven difficult. Given that invertebrate central pattern generators so often depend on both chemical and electrical synapses, our hypothesis is that hippocampus-mediated and -influenced behaviors will act likewise. Experiments, likely hard ones, will be required to test this intuition.
Collapse
Affiliation(s)
- Roger D Traub
- Department of Physical Sciences, IBM T.J. Watson Research Center, Yorktown Heights, NY, 10598, USA.
| | | | - Rafael Gutiérrez
- Department of Pharmacobiology, Centro de Investigación y de Estudios Avanzados del IPN, Calzada de los Tenorios 235, 14330, Mexico City, Mexico.,Institut für Physiologie und Pathophysiologie, Universität Heidelberg, Im Neuenheimer Feld 326, 69120, Heidelberg, Germany
| | - Andreas Draguhn
- Institut für Physiologie und Pathophysiologie, Universität Heidelberg, Im Neuenheimer Feld 326, 69120, Heidelberg, Germany
| |
Collapse
|
10
|
Alcami P. Electrical Synapses Enhance and Accelerate Interneuron Recruitment in Response to Coincident and Sequential Excitation. Front Cell Neurosci 2018; 12:156. [PMID: 29973871 PMCID: PMC6020792 DOI: 10.3389/fncel.2018.00156] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 05/17/2018] [Indexed: 01/17/2023] Open
Abstract
Electrical synapses are ubiquitous in interneuron networks. They form intercellular pathways, allowing electrical currents to leak between coupled interneurons. I explored the impact of electrical coupling on the integration of excitatory signals and on the coincidence detection abilities of electrically-coupled cerebellar basket cells (BCs). In order to do so, I quantified the influence of electrical coupling on the rate, the probability and the latency at which BCs generate action potentials when stimulated. The long-lasting simultaneous suprathreshold depolarization of a coupled cell evoked an increase in firing rate and a shortening of action potential latency in a reference basket cell, compared to its depolarization alone. Likewise, the action potential probability of coupled cells was strongly increased when they were simultaneously stimulated with trains of short-duration near-threshold current pulses (mimicking the activation of presynaptic granule cells) at 10 Hz, and to a lesser extent at 50 Hz, an effect that was absent in non-coupled cells. Moreover, action potential probability was increased and action potential latency was shortened in response to synaptic stimulations in mice lacking the protein that forms gap junctions between BCs, connexin36, relative to wild-type (WT) controls. These results suggest that electrical synapses between BCs decrease the probability and increase the latency of stimulus-triggered action potentials, both effects being reverted upon simultaneous excitation of coupled cells. Interestingly, varying the delay at which coupled cells are stimulated revealed that the probability and the speed of action potential generation are facilitated maximally when a basket cell is stimulated shortly after a coupled cell. These findings suggest that electrically-coupled interneurons behave as coincidence and sequence detectors that dynamically regulate the latency and the strength of inhibition onto postsynaptic targets depending on the degree of input synchrony in the coupled interneuron network.
Collapse
Affiliation(s)
- Pepe Alcami
- Laboratoire de Physiologie Cérébrale, Unité Mixte de Recherche UMR8118, Université Paris Descartes and Centre National de la Recherche Scientifique, Paris, France.,Laboratory of Cellular and Systemic Neurophysiology, Institute for Physiology I, Albert-Ludwigs University Freiburg, Freiburg, Germany.,Grass Laboratory, Marine Biological Laboratory, Woods Hole, MA, United States.,Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| |
Collapse
|
11
|
Pelkey KA, Chittajallu R, Craig MT, Tricoire L, Wester JC, McBain CJ. Hippocampal GABAergic Inhibitory Interneurons. Physiol Rev 2017; 97:1619-1747. [PMID: 28954853 DOI: 10.1152/physrev.00007.2017] [Citation(s) in RCA: 481] [Impact Index Per Article: 68.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 05/16/2017] [Accepted: 05/26/2017] [Indexed: 12/11/2022] Open
Abstract
In the hippocampus GABAergic local circuit inhibitory interneurons represent only ~10-15% of the total neuronal population; however, their remarkable anatomical and physiological diversity allows them to regulate virtually all aspects of cellular and circuit function. Here we provide an overview of the current state of the field of interneuron research, focusing largely on the hippocampus. We discuss recent advances related to the various cell types, including their development and maturation, expression of subtype-specific voltage- and ligand-gated channels, and their roles in network oscillations. We also discuss recent technological advances and approaches that have permitted high-resolution, subtype-specific examination of their roles in numerous neural circuit disorders and the emerging therapeutic strategies to ameliorate such pathophysiological conditions. The ultimate goal of this review is not only to provide a touchstone for the current state of the field, but to help pave the way for future research by highlighting where gaps in our knowledge exist and how a complete appreciation of their roles will aid in future therapeutic strategies.
Collapse
Affiliation(s)
- Kenneth A Pelkey
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Ramesh Chittajallu
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Michael T Craig
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Ludovic Tricoire
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Jason C Wester
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Chris J McBain
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| |
Collapse
|
12
|
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: 4.0] [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.
Collapse
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.
| |
Collapse
|
13
|
O'Brien J. Design principles of electrical synaptic plasticity. Neurosci Lett 2017; 695:4-11. [PMID: 28893590 DOI: 10.1016/j.neulet.2017.09.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 08/09/2017] [Accepted: 09/01/2017] [Indexed: 01/19/2023]
Abstract
Essentially all animals with nervous systems utilize electrical synapses as a core element of communication. Electrical synapses, formed by gap junctions between neurons, provide rapid, bidirectional communication that accomplishes tasks distinct from and complementary to chemical synapses. These include coordination of neuron activity, suppression of voltage noise, establishment of electrical pathways that define circuits, and modulation of high order network behavior. In keeping with the omnipresent demand to alter neural network function in order to respond to environmental cues and perform tasks, electrical synapses exhibit extensive plasticity. In some networks, this plasticity can have dramatic effects that completely remodel circuits or remove the influence of certain cell types from networks. Electrical synaptic plasticity occurs on three distinct time scales, ranging from milliseconds to days, with different mechanisms accounting for each. This essay highlights principles that dictate the properties of electrical coupling within networks and the plasticity of the electrical synapses, drawing examples extensively from retinal networks.
Collapse
Affiliation(s)
- John O'Brien
- McGovern Medical School, The University of Texas Health Science Center at Houston, 6431 Fannin St., MSB 7.024, Houston, TX 77030, USA.
| |
Collapse
|
14
|
Role of Somatostatin-Positive Cortical Interneurons in the Generation of Sleep Slow Waves. J Neurosci 2017; 37:9132-9148. [PMID: 28821651 DOI: 10.1523/jneurosci.1303-17.2017] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 07/03/2017] [Accepted: 08/08/2017] [Indexed: 02/05/2023] Open
Abstract
During non-rapid eye-movement (NREM) sleep, cortical and thalamic neurons oscillate every second or so between ON periods, characterized by membrane depolarization and wake-like tonic firing, and OFF periods, characterized by membrane hyperpolarization and neuronal silence. Cortical slow waves, the hallmark of NREM sleep, reflect near-synchronous OFF periods in cortical neurons. However, the mechanisms triggering such OFF periods are unclear, as there is little evidence for somatic inhibition. We studied cortical inhibitory interneurons that express somatostatin (SOM), because ∼70% of them are Martinotti cells that target diffusely layer I and can block excitatory transmission presynaptically, at glutamatergic terminals, and postsynaptically, at apical dendrites, without inhibiting the soma. In freely moving male mice, we show that SOM+ cells can fire immediately before slow waves and their optogenetic stimulation during ON periods of NREM sleep triggers long OFF periods. Next, we show that chemogenetic activation of SOM+ cells increases slow-wave activity (SWA), slope of individual slow waves, and NREM sleep duration; whereas their chemogenetic inhibition decreases SWA and slow-wave incidence without changing time spent in NREM sleep. By contrast, activation of parvalbumin+ (PV+) cells, the most numerous population of cortical inhibitory neurons, greatly decreases SWA and cortical firing, triggers short OFF periods in NREM sleep, and increases NREM sleep duration. Thus SOM+ cells, but not PV+ cells, are involved in the generation of sleep slow waves. Whether Martinotti cells are solely responsible for this effect, or are complemented by other classes of inhibitory neurons, remains to be investigated.SIGNIFICANCE STATEMENT Cortical slow waves are a defining feature of non-rapid eye-movement (NREM) sleep and are thought to be important for many of its restorative benefits. Yet, the mechanism by which cortical neurons abruptly and synchronously cease firing, the neuronal basis of the slow wave, remains unknown. Using chemogenetic and optogenetic approaches, we provide the first evidence that links a specific class of inhibitory interneurons-somatostatin-positive cells-to the generation of slow waves during NREM sleep in freely moving mice.
Collapse
|
15
|
Mathews J, Levin M. Gap junctional signaling in pattern regulation: Physiological network connectivity instructs growth and form. Dev Neurobiol 2017; 77:643-673. [PMID: 27265625 PMCID: PMC10478170 DOI: 10.1002/dneu.22405] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 05/27/2016] [Accepted: 05/31/2016] [Indexed: 12/19/2022]
Abstract
Gap junctions (GJs) are aqueous channels that allow cells to communicate via physiological signals directly. The role of gap junctional connectivity in determining single-cell functions has long been recognized. However, GJs have another important role: the regulation of large-scale anatomical pattern. GJs are not only versatile computational elements that allow cells to control which small molecule signals they receive and emit, but also establish connectivity patterns within large groups of cells. By dynamically regulating the topology of bioelectric networks in vivo, GJs underlie the ability of many tissues to implement complex morphogenesis. Here, a review of recent data on patterning roles of GJs in growth of the zebrafish fin, the establishment of left-right patterning, the developmental dysregulation known as cancer, and the control of large-scale head-tail polarity, and head shape in planarian regeneration has been reported. A perspective in which GJs are not only molecular features functioning in single cells, but also enable global neural-like dynamics in non-neural somatic tissues has been proposed. This view suggests a rich program of future work which capitalizes on the rapid advances in the biophysics of GJs to exploit GJ-mediated global dynamics for applications in birth defects, regenerative medicine, and morphogenetic bioengineering. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 643-673, 2017.
Collapse
Affiliation(s)
- Juanita Mathews
- Department of Biology, Tufts Center for Regenerative and Developmental Biology, Tufts University, Medford, MA
| | - Michael Levin
- Department of Biology, Tufts Center for Regenerative and Developmental Biology, Tufts University, Medford, MA
| |
Collapse
|
16
|
Miller AC, Pereda AE. The electrical synapse: Molecular complexities at the gap and beyond. Dev Neurobiol 2017; 77:562-574. [PMID: 28170151 DOI: 10.1002/dneu.22484] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/04/2017] [Accepted: 01/04/2017] [Indexed: 12/21/2022]
Abstract
Gap junctions underlie electrical synaptic transmission between neurons. Generally perceived as simple intercellular channels, "electrical synapses" have demonstrated to be more functionally sophisticated and structurally complex than initially anticipated. Electrical synapses represent an assembly of multiple molecules, consisting of channels, adhesion complexes, scaffolds, regulatory machinery, and trafficking proteins, all required for their proper function and plasticity. Additionally, while electrical synapses are often viewed as strictly symmetric structures, emerging evidence has shown that some components forming electrical synapses can be differentially distributed at each side of the junction. We propose that the molecular complexity and asymmetric distribution of proteins at the electrical synapse provides rich potential for functional diversity. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 562-574, 2017.
Collapse
Affiliation(s)
- Adam C Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| |
Collapse
|
17
|
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: 48] [Impact Index Per Article: 6.9] [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.
Collapse
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.
| |
Collapse
|
18
|
Villette V, Guigue P, Picardo MA, Sousa VH, Leprince E, Lachamp P, Malvache A, Tressard T, Cossart R, Baude A. Development of early-born γ-Aminobutyric acid hub neurons in mouse hippocampus from embryogenesis to adulthood. J Comp Neurol 2016; 524:2440-61. [PMID: 26779909 PMCID: PMC4949683 DOI: 10.1002/cne.23961] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 12/04/2015] [Accepted: 01/03/2016] [Indexed: 02/02/2023]
Abstract
Early‐born γ‐aminobutyric acid (GABA) neurons (EBGNs) are major components of the hippocampal circuit because at early postnatal stages they form a subpopulation of “hub cells” transiently supporting CA3 network synchronization (Picardo et al. [2011] Neuron 71:695–709). It is therefore essential to determine when these cells acquire the remarkable morphofunctional attributes supporting their network function and whether they develop into a specific subtype of interneuron into adulthood. Inducible genetic fate mapping conveniently allows for the labeling of EBGNs throughout their life. EBGNs were first analyzed during the perinatal week. We observed that EBGNs acquired mature characteristics at the time when the first synapse‐driven synchronous activities appeared in the form of giant depolarizing potentials. The fate of EBGNs was next analyzed in the adult hippocampus by using anatomical characterization. Adult EBGNs included a significant proportion of cells projecting selectively to the septum; in turn, EBGNs were targeted by septal and entorhinal inputs. In addition, most EBGNs were strongly targeted by cholinergic and monoaminergic terminals, suggesting significant subcortical innervation. Finally, we found that some EBGNs located in the septum or the entorhinal cortex also displayed a long‐range projection that we traced to the hippocampus. Therefore, this study shows that the maturation of the morphophysiological properties of EBGNs mirrors the evolution of early network dynamics, suggesting that both phenomena may be causally linked. We propose that a subpopulation of EBGNs forms into adulthood a scaffold of GABAergic projection neurons linking the hippocampus to distant structures. J. Comp. Neurol. 524:2440–2461, 2016. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Vincent Villette
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Philippe Guigue
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Michel Aimé Picardo
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Vitor Hugo Sousa
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Erwan Leprince
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Philippe Lachamp
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Arnaud Malvache
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Thomas Tressard
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Rosa Cossart
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| | - Agnès Baude
- INSERM U901, Marseille, 13009, France.,Aix-Marseille University, UMR 901, Marseille, 13009, France.,INMED, Marseille, 13009, France
| |
Collapse
|
19
|
Abstract
Altered inhibitory function is an important facet of epileptic pathology. A key concept is that GABAergic activity can become excitatory if intraneuronal chloride rises. However, it has proved difficult to separate the role of raised chloride from other contributory factors in complex network phenomena, such as epileptic pathology. Therefore, we asked what patterns of activity are associated with chloride dysregulation by making novel use of Halorhodopsin to load clusters of mouse pyramidal cells artificially with Cl(-). Brief (1-10 s) activation of Halorhodopsin caused substantial positive shifts in the GABAergic reversal potential that were proportional to the charge transfer during the illumination and in adult neocortical pyramidal neurons decayed with a time constant of τ = 8.0 ± 2.8s. At the network level, these positive shifts in EGABA produced a transient rise in network excitability, with many distinctive features of epileptic foci, including high-frequency oscillations with evidence of out-of-phase firing (Ibarz et al., 2010). We show how such firing patterns can arise from quite small shifts in the mean intracellular Cl(-) level, within heterogeneous neuronal populations. Notably, however, chloride loading by itself did not trigger full ictal events, even with additional electrical stimulation to the underlying white matter. In contrast, when performed in combination with low, subepileptic levels of 4-aminopyridine, Halorhodopsin activation rapidly induced full ictal activity. These results suggest that chloride loading has at most an adjunctive role in ictogenesis. Our simulations also show how chloride loading can affect the jitter of action potential timing associated with imminent recruitment to an ictal event (Netoff and Schiff, 2002).
Collapse
|
20
|
Activation of Group I and Group II Metabotropic Glutamate Receptors Causes LTD and LTP of Electrical Synapses in the Rat Thalamic Reticular Nucleus. J Neurosci 2015; 35:7616-25. [PMID: 25972185 DOI: 10.1523/jneurosci.3688-14.2015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Compared with the extensive characterization of chemical synaptic plasticity, electrical synaptic plasticity remains poorly understood. Electrical synapses are strong and prevalent among the GABAergic neurons of the rodent thalamic reticular nucleus. Using paired whole-cell recordings, we show that activation of Group I metabotropic glutamate receptors (mGluRs) induces long-term depression of electrical synapses. Conversely, activation of the Group II mGluR, mGluR3, induces long-term potentiation of electrical synapses. By testing downstream targets, we show that modifications induced by both mGluR groups converge on the same signaling cascade--adenylyl cyclase to cAMP to protein kinase A--but with opposing effects. Furthermore, the magnitude of modification is inversely correlated to baseline coupling strength. Thus, electrical synapses, like their chemical counterparts, undergo both strengthening and weakening forms of plasticity, which should play a significant role in thalamocortical function.
Collapse
|
21
|
Electrical synapses connect a network of gonadotropin releasing hormone neurons in a cichlid fish. Proc Natl Acad Sci U S A 2015; 112:3805-10. [PMID: 25775522 DOI: 10.1073/pnas.1421851112] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Initiating and regulating vertebrate reproduction requires pulsatile release of gonadotropin-releasing hormone (GnRH1) from the hypothalamus. Coordinated GnRH1 release, not simply elevated absolute levels, effects the release of pituitary gonadotropins that drive steroid production in the gonads. However, the mechanisms underlying synchronization of GnRH1 neurons are unknown. Control of synchronicity by gap junctions between GnRH1 neurons has been proposed but not previously found. We recorded simultaneously from pairs of transgenically labeled GnRH1 neurons in adult male Astatotilapia burtoni cichlid fish. We report that GnRH1 neurons are strongly and uniformly interconnected by electrical synapses that can drive spiking in connected cells and can be reversibly blocked by meclofenamic acid. Our results suggest that electrical synapses could promote coordinated spike firing in a cellular assemblage of GnRH1 neurons to produce the pulsatile output necessary for activation of the pituitary and reproduction.
Collapse
|
22
|
Transiently increasing cAMP levels selectively in hippocampal excitatory neurons during sleep deprivation prevents memory deficits caused by sleep loss. J Neurosci 2015; 34:15715-21. [PMID: 25411499 DOI: 10.1523/jneurosci.2403-14.2014] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The hippocampus is particularly sensitive to sleep loss. Although previous work has indicated that sleep deprivation impairs hippocampal cAMP signaling, it remains to be determined whether the cognitive deficits associated with sleep deprivation are caused by attenuated cAMP signaling in the hippocampus. Further, it is unclear which cell types are responsible for the memory impairments associated with sleep deprivation. Transgenic approaches lack the spatial resolution to manipulate specific signaling pathways selectively in the hippocampus, while pharmacological strategies are limited in terms of cell-type specificity. Therefore, we used a pharmacogenetic approach based on a virus-mediated expression of a Gαs-coupled Drosophila octopamine receptor selectively in mouse hippocampal excitatory neurons in vivo. With this approach, a systemic injection with the receptor ligand octopamine leads to increased cAMP levels in this specific set of hippocampal neurons. We assessed whether transiently increasing cAMP levels during sleep deprivation prevents memory consolidation deficits associated with sleep loss in an object-location task. Five hours of total sleep deprivation directly following training impaired the formation of object-location memories. Transiently increasing cAMP levels in hippocampal neurons during the course of sleep deprivation prevented these memory consolidation deficits. These findings demonstrate that attenuated cAMP signaling in hippocampal excitatory neurons is a critical component underlying the memory deficits in hippocampus-dependent learning tasks associated with sleep deprivation.
Collapse
|
23
|
Nadim F, Bucher D. Neuromodulation of neurons and synapses. Curr Opin Neurobiol 2014; 29:48-56. [PMID: 24907657 DOI: 10.1016/j.conb.2014.05.003] [Citation(s) in RCA: 167] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 05/09/2014] [Accepted: 05/09/2014] [Indexed: 12/15/2022]
Abstract
Neuromodulation underlies the flexibility of neural circuit operation and behavior. Individual neuromodulators can have divergent actions in a neuron by targeting multiple physiological mechanisms. Conversely, multiple neuromodulators may have convergent actions through overlapping targets. The divergent and convergent neuromodulator actions can be unambiguously synergistic or antagonistic, but neuromodulation often entails balanced adjustment of nonlinear membrane and synaptic properties by targeting ion channel and synaptic dynamics rather than just excitability or synaptic strength. In addition, neuromodulators can exert effects at multiple timescales, from short-term adjustments of neuron and synapse function to persistent long-term regulation. This short review summarizes some highlights of the diverse actions of neuromodulators on ion channel and synaptic properties.
Collapse
Affiliation(s)
- Farzan Nadim
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University, 323 Martin Luther King Blvd, Newark, NJ 07102, United States.
| | - Dirk Bucher
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University, 323 Martin Luther King Blvd, Newark, NJ 07102, United States
| |
Collapse
|
24
|
Posłuszny A. The contribution of electrical synapses to field potential oscillations in the hippocampal formation. Front Neural Circuits 2014; 8:32. [PMID: 24772068 PMCID: PMC3982077 DOI: 10.3389/fncir.2014.00032] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 03/18/2014] [Indexed: 11/23/2022] Open
Abstract
Electrical synapses are a type of cellular membrane junction referred to as gap junctions (GJs). They provide a direct way to exchange ions between coupled cells and have been proposed as a structural basis for fast transmission of electrical potentials between neurons in the brain. For this reason GJs have been regarded as an important component within the neuronal networks that underlie synchronous neuronal activity and field potential oscillations. Initially, GJs appeared to play a particularly key role in the generation of high frequency oscillatory patterns in field potentials. In order to assess the scale of neuronal GJs contribution to field potential oscillations in the hippocampal formation, in vivo and in vitro studies are reviewed here. These investigations have shown that blocking the main neuronal GJs, those containing connexin 36 (Cx36-GJs), or knocking out the Cx36 gene affect field potential oscillatory patterns related to awake active behavior (gamma and theta rhythm) but have no effect on high frequency oscillations occurring during silent wake and sleep. Precisely how Cx36-GJs influence population activity of neurons is more complex than previously thought. Analysis of studies on the properties of transmission through GJ channels as well as Cx36-GJs functioning in pairs of coupled neurons provides some explanations of the specific influence of Cx36-GJs on field potential oscillations. It is proposed here that GJ transmission is strongly modulated by the level of neuronal network activity and changing behavioral states. Therefore, contribution of GJs to field potential oscillatory patterns depends on the behavioral state. I propose here a model, based on large body of experimental data gathered in this field by several authors, in which Cx36-GJ transmission especially contributes to oscillations related to active behavior, where it plays a role in filtering and enhancing coherent signals in the network under high-noise conditions. In contrast, oscillations related to silent wake or sleep, especially high frequency oscillations, do not require transmission by neuronal GJs. The reliability of neuronal discharges during those oscillations could be assured by conditions of higher signal-to-noise ratio and some synaptic changes taking place during active behavior.
Collapse
Affiliation(s)
- Anna Posłuszny
- Laboratory of Neuroplasticity, Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences Warsaw, Poland
| |
Collapse
|
25
|
Electrical synapses and their functional interactions with chemical synapses. Nat Rev Neurosci 2014; 15:250-63. [PMID: 24619342 DOI: 10.1038/nrn3708] [Citation(s) in RCA: 297] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Brain function relies on the ability of neurons to communicate with each other. Interneuronal communication primarily takes place at synapses, where information from one neuron is rapidly conveyed to a second neuron. There are two main modalities of synaptic transmission: chemical and electrical. Far from functioning independently and serving unrelated functions, mounting evidence indicates that these two modalities of synaptic transmission closely interact, both during development and in the adult brain. Rather than conceiving synaptic transmission as either chemical or electrical, this article emphasizes the notion that synaptic transmission is both chemical and electrical, and that interactions between these two forms of interneuronal communication might be required for normal brain development and function.
Collapse
|
26
|
Meyrand P, Bem T. Variety of alternative stable phase-locking in networks of electrically coupled relaxation oscillators. PLoS One 2014; 9:e86572. [PMID: 24520321 PMCID: PMC3919711 DOI: 10.1371/journal.pone.0086572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 12/12/2013] [Indexed: 11/22/2022] Open
Abstract
We studied the dynamics of a large-scale model network comprised of oscillating electrically coupled neurons. Cells are modeled as relaxation oscillators with short duty cycle, so they can be considered either as models of pacemaker cells, spiking cells with fast regenerative and slow recovery variables or firing rate models of excitatory cells with synaptic depression or cellular adaptation. It was already shown that electrically coupled relaxation oscillators exhibit not only synchrony but also anti-phase behavior if electrical coupling is weak. We show that a much wider spectrum of spatiotemporal patterns of activity can emerge in a network of electrically coupled cells as a result of switching from synchrony, produced by short external signals of different spatial profiles. The variety of patterns increases with decreasing rate of neuronal firing (or duty cycle) and with decreasing strength of electrical coupling. We study also the effect of network topology - from all-to-all – to pure ring connectivity, where only the closest neighbors are coupled. We show that the ring topology promotes anti-phase behavior as compared to all-to-all coupling. It also gives rise to a hierarchical organization of activity: during each of the main phases of a given pattern cells fire in a particular sequence determined by the local connectivity. We have analyzed the behavior of the network using geometric phase plane methods and we give heuristic explanations of our findings. Our results show that complex spatiotemporal activity patterns can emerge due to the action of stochastic or sensory stimuli in neural networks without chemical synapses, where each cell is equally coupled to others via gap junctions. This suggests that in developing nervous systems where only electrical coupling is present such a mechanism can lead to the establishment of proto-networks generating premature multiphase oscillations whereas the subsequent emergence of chemical synapses would later stabilize generated patterns.
Collapse
Affiliation(s)
- Pierre Meyrand
- Univ. Bordeaux, IMN, UMR 5293, Bordeaux, France
- CNRS, IMN, UMR 5293, Bordeaux, France
- * E-mail:
| | - Tiaza Bem
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland
| |
Collapse
|
27
|
Olejarczyk E, Ostaszewski H, Meyrand P, Bem T. Susceptibility of switching between in-phase and anti-phase patterns in the network of relaxation oscillators. Biocybern Biomed Eng 2014. [DOI: 10.1016/j.bbe.2014.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
28
|
Dynamic tuning of electrical and chemical synaptic transmission in a network of motion coding retinal neurons. J Neurosci 2013; 33:14927-38. [PMID: 24027292 DOI: 10.1523/jneurosci.0808-13.2013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recently, we demonstrated that gap junction coupling in the population of superior coding ON-OFF directionally selective ganglion cells (DSGCs) genetically labeled in the Hb9::eGFP mouse retina allows the passage of lateral anticipatory signals that help track moving stimuli. Here, we examine the properties of gap junctions in the DSGC network, and address how interactions between electrical and chemical synapses and intrinsic membrane properties contribute to the dynamic tuning of lateral anticipatory signals. When DSGC subtypes coding all four cardinal directions were individually loaded with the gap junction-permeable tracer Neurobiotin, only superior coding DSGCs exhibited homologous coupling. Consistent with these anatomical findings, gap junction-dependent feedback spikelets were only observed in Hb9(+) DSGCs. Recordings from pairs of neighboring Hb9(+) DSGCs revealed that coupling was reciprocal, non-inactivating, and relatively weak, and provided a substrate for an extensive subthreshold excitatory receptive field around each cell. This subthreshold activity appeared to boost coincident light-driven chemical synaptic responses. However, during responses to moving stimuli, gap junction-mediated boosting appeared to be dynamically modulated such that upstream DSGCs primed downstream cells, but not vice versa, giving rise to highly skewed responses in individual cells. We show that the asymmetry in priming arises from a combination of spatially offset GABAergic inhibition and activity-dependent changes in intrinsic membrane properties of DSGCs. Thus, dynamic interactions between electrical and chemical synapses and intrinsic membrane properties allow the network of DSGCs to propagate anticipatory responses most effectively along their preferred direction without leading to runaway excitation.
Collapse
|
29
|
Bidirectional modulation of hippocampal gamma (20–80Hz) frequency activity in vitro via alpha(α)- and beta(β)-adrenergic receptors (AR). Neuroscience 2013; 253:142-54. [DOI: 10.1016/j.neuroscience.2013.08.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 08/09/2013] [Accepted: 08/18/2013] [Indexed: 11/24/2022]
|
30
|
Liu Y, Liang X, Ren WW, Li BM. Expression of β1- and β2-adrenoceptors in different subtypes of interneurons in the medial prefrontal cortex of mice. Neuroscience 2013; 257:149-57. [PMID: 24215978 DOI: 10.1016/j.neuroscience.2013.10.078] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Revised: 10/17/2013] [Accepted: 10/30/2013] [Indexed: 02/02/2023]
Abstract
Noradrenaline acting via β-adrenoceptors (β-ARs) in the CNS plays an important role in learning/memory and cognitive functions. β-ARs have been shown to be expressed in cortical pyramidal and subcortical principal cells. However, little is known about β-AR expression in different subtypes of GABAergic neurons. Here, we report that both β1- and β2-ARs are expressed in a majority of GABAergic interneurons in the medial prefrontal cortex of mice, including parvalbumin (PV)-, calretinin (CR)-, calbindin D-28k (CB)-, somatostatin (SST)- and Reelin-immunoreactive (ir) interneurons. Relative to PV-, CB-, SST- and Reelin-ir interneurons, CR-ir interneurons are less likely to express β1- and β2-ARs. SST-ir interneurons are more likely to express β2-AR compared with the other subtypes of interneurons. The present results are of significance for understanding the role of β-ARs in prefrontal cortical functions.
Collapse
Affiliation(s)
- Y Liu
- Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Fudan University, Shanghai 200032, China
| | - X Liang
- Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Fudan University, Shanghai 200032, China
| | - W-W Ren
- Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Fudan University, Shanghai 200032, China
| | - B-M Li
- Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Fudan University, Shanghai 200032, China; Center for Neuropsychiatric Disorders, Institute of Life Science, Nanchang University, Nanchang 330031, China.
| |
Collapse
|
31
|
Belousov AB, Fontes JD. Neuronal gap junctions: making and breaking connections during development and injury. Trends Neurosci 2013; 36:227-36. [PMID: 23237660 PMCID: PMC3609876 DOI: 10.1016/j.tins.2012.11.001] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 11/02/2012] [Accepted: 11/02/2012] [Indexed: 01/08/2023]
Abstract
In the mammalian central nervous system (CNS), coupling of neurons by gap junctions (i.e., electrical synapses) and the expression of the neuronal gap junction protein, connexin 36 (Cx36), transiently increase during early postnatal development. The levels of both subsequently decline and remain low in the adult, confined to specific subsets of neurons. However, following neuronal injury [such as ischemia, traumatic brain injury (TBI), and epilepsy], the coupling and expression of Cx36 rise. Here we summarize new findings on the mechanisms of regulation of Cx36-containing gap junctions in the developing and mature CNS and following injury. We also review recent studies suggesting various roles for neuronal gap junctions and in particular their role in glutamate-mediated neuronal death.
Collapse
Affiliation(s)
- Andrei B Belousov
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
| | | |
Collapse
|
32
|
Haas JS, Landisman CE. Bursts modify electrical synaptic strength. Brain Res 2012; 1487:140-9. [PMID: 22771703 PMCID: PMC3501583 DOI: 10.1016/j.brainres.2012.05.061] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 05/09/2012] [Indexed: 11/16/2022]
Abstract
Changes in synaptic strength resulting from neuronal activity have been described in great detail for chemical synapses, but the relationship between natural forms of activity and the strength of electrical synapses had previously not been investigated. The thalamic reticular nucleus (TRN), a brain area rich in gap junctional (electrical) synapses, regulates cortical attention, initiates sleep spindles, and participates in shifts between states of arousal. Plasticity of electrical synapses in the TRN may be a key mechanism underlying these processes. Recently, we demonstrated a novel activity-dependent form of long-term depression of electrical synapses in the TRN (Haas et al., 2011). Here we provide an overview of those findings and discuss them in broader context. Because gap junctional proteins are widely expressed in the mammalian brain, modification of synaptic strength is likely to be a widespread and powerful mechanism at electrical synapses throughout the brain.
Collapse
Affiliation(s)
- Julie S Haas
- Center for Brain Science, Harvard University, 52 Oxford St. NWL 202, Cambridge, MA 02138, USA.
| | | |
Collapse
|
33
|
Hervé JC, Derangeon M. Gap-junction-mediated cell-to-cell communication. Cell Tissue Res 2012; 352:21-31. [PMID: 22940728 DOI: 10.1007/s00441-012-1485-6] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 08/01/2012] [Indexed: 11/26/2022]
Abstract
Cells of multicellular organisms need to communicate with each other and have evolved various mechanisms for this purpose, the most direct and quickest of which is through channels that directly connect the cytoplasms of adjacent cells. Such intercellular channels span the two plasma membranes and the intercellular space and result from the docking of two hemichannels. These channels are densely packed into plasma-membrane spatial microdomains termed "gap junctions" and allow cells to exchange ions and small molecules directly. A hemichannel is a hexameric torus of junctional proteins around an aqueous pore. Vertebrates express two families of gap-junction proteins: the well-characterized connexins and the more recently discovered pannexins, the latter being related to invertebrate innexins ("invertebrate connexins"). Some gap-junctional hemichannels also appear to mediate cell-extracellular communication. Communicating junctions play crucial roles in the maintenance of homeostasis, morphogenesis, cell differentiation and growth control in metazoans. Gap-junctional channels are not passive conduits, as previously long regarded, but use "gating" mechanisms to open and close the central pore in response to biological stimuli (e.g. a change in the transjunctional voltage). Their permeability is finely tuned by complex mechanisms that have just begun to be identified. Given their ubiquity and diversity, gap junctions play crucial roles in a plethora of functions and their dysfunctions are involved in a wide range of diseases. However, the exact mechanisms involved remain poorly understood.
Collapse
Affiliation(s)
- Jean-Claude Hervé
- Institut de Physiologie et Biologie Cellulaires, FRE3511, Université de Poitiers, CNRS, 1 Rue Georges Bonnet, Poitiers, 86022, France.
| | | |
Collapse
|
34
|
Hartveit E, Veruki ML. Electrical synapses between AII amacrine cells in the retina: Function and modulation. Brain Res 2012; 1487:160-72. [PMID: 22776293 DOI: 10.1016/j.brainres.2012.05.060] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 05/09/2012] [Indexed: 12/24/2022]
Abstract
Adaptation enables the visual system to operate across a large range of background light intensities. There is evidence that one component of this adaptation is mediated by modulation of gap junctions functioning as electrical synapses, thereby tuning and functionally optimizing specific retinal microcircuits and pathways. The AII amacrine cell is an interneuron found in most mammalian retinas and plays a crucial role for processing visual signals in starlight, twilight and daylight. AII amacrine cells are connected to each other by gap junctions, potentially serving as a substrate for signal averaging and noise reduction, and there is evidence that the strength of electrical coupling is modulated by the level of background light. Whereas there is extensive knowledge concerning the retinal microcircuits that involve the AII amacrine cell, it is less clear which signaling pathways and intracellular transduction mechanisms are involved in modulating the junctional conductance between electrically coupled AII amacrine cells. Here we review the current state of knowledge, with a focus on the recent evidence that suggests that the modulatory control involves activity-dependent changes in the phosphorylation of the gap junction channels between AII amacrine cells, potentially linked to their intracellular Ca(2+) dynamics. This article is part of a Special Issue entitled Electrical Synapses.
Collapse
Affiliation(s)
- Espen Hartveit
- University of Bergen, Department of Biomedicine, Bergen, Norway.
| | | |
Collapse
|
35
|
Cachope R, Pereda AE. Two independent forms of activity-dependent potentiation regulate electrical transmission at mixed synapses on the Mauthner cell. Brain Res 2012; 1487:173-82. [PMID: 22771708 DOI: 10.1016/j.brainres.2012.05.059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 04/24/2012] [Accepted: 05/09/2012] [Indexed: 10/28/2022]
Abstract
Mixed (electrical and chemical) synaptic contacts on the Mauthner cells, known as Club endings, constitute a valuable model for the study of vertebrate electrical transmission. While electrical synapses are still perceived by many as passive intercellular channels that lack modifiability, a wealth of experimental evidence shows that gap junctions at Club endings are subject to dynamic regulatory control by two independent activity-dependent mechanisms that lead to potentiation of electrical transmission. One of those mechanisms relies on activation of NMDA receptors and postsynaptic CaMKII. A second mechanism relies on mGluR activation and endocannabinoid production and is indirectly mediated via the release of dopamine from nearby varicosities, which in turn leads to potentiation of the synaptic response via a PKA-mediated postsynaptic mechanism. We review here these two forms of potentiation and their signaling mechanisms, which include the activation of two kinases with well-established roles as regulators of synaptic strength, as well as the functional implications of these two forms of potentiation. Special Issue entitled Electrical Synapses.
Collapse
Affiliation(s)
- Roger Cachope
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine of Yeshiva University, Bronx, NY 10461, USA
| | | |
Collapse
|
36
|
Pereda AE, Curti S, Hoge G, Cachope R, Flores CE, Rash JE. Gap junction-mediated electrical transmission: regulatory mechanisms and plasticity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:134-46. [PMID: 22659675 DOI: 10.1016/j.bbamem.2012.05.026] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 05/16/2012] [Accepted: 05/23/2012] [Indexed: 02/08/2023]
Abstract
The term synapse applies to cellular specializations that articulate the processing of information within neural circuits by providing a mechanism for the transfer of information between two different neurons. There are two main modalities of synaptic transmission: chemical and electrical. While most efforts have been dedicated to the understanding of the properties and modifiability of chemical transmission, less is still known regarding the plastic properties of electrical synapses, whose structural correlate is the gap junction. A wealth of data indicates that, rather than passive intercellular channels, electrical synapses are more dynamic and modifiable than was generally perceived. This article will discuss the factors determining the strength of electrical transmission and review current evidence demonstrating its dynamic properties. Like their chemical counterparts, electrical synapses can also be plastic and modifiable. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.
Collapse
Affiliation(s)
- Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.
| | | | | | | | | | | |
Collapse
|
37
|
Armstrong C, Krook-Magnuson E, Soltesz I. Neurogliaform and Ivy Cells: A Major Family of nNOS Expressing GABAergic Neurons. Front Neural Circuits 2012; 6:23. [PMID: 22623913 PMCID: PMC3353154 DOI: 10.3389/fncir.2012.00023] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 04/13/2012] [Indexed: 12/05/2022] Open
Abstract
Neurogliaform and Ivy cells are members of an abundant family of neuronal nitric oxide synthase (nNOS) expressing GABAergic interneurons found in diverse brain regions. These cells have a defining dense local axonal plexus, and display unique synaptic properties including a biphasic postsynaptic response with both a slow GABA(A) component and a GABA(B) component following even a single action potential. The type of transmission displayed by these cells has been termed "volume transmission," distinct from both tonic and classical synaptic transmission. Electrical connections are also notable in that, unlike other GABAergic cell types, neurogliaform family cells will form gap junctions not only with other neurogliaform cells, but also with non-neurogliaform family GABAergic cells. In this review, we focus on neurogliaform and Ivy cells throughout the hippocampal formation, where recent studies highlight their role in feedforward inhibition, uncover their ability to display a phenomenon called persistent firing, and reveal their modulation by opioids. The unique properties of this family of cells, their abundance, rich connectivity, and modulation by clinically relevant drugs make them an attractive target for future studies in vivo during different behavioral and pharmacological conditions.
Collapse
Affiliation(s)
- Caren Armstrong
- Department of Anatomy and Neurobiology, University of California IrvineIrvine, CA, USA
| | - Esther Krook-Magnuson
- Department of Anatomy and Neurobiology, University of California IrvineIrvine, CA, USA
| | - Ivan Soltesz
- Department of Anatomy and Neurobiology, University of California IrvineIrvine, CA, USA
| |
Collapse
|
38
|
Kothmann WW, Trexler EB, Whitaker CM, Li W, Massey SC, O'Brien J. Nonsynaptic NMDA receptors mediate activity-dependent plasticity of gap junctional coupling in the AII amacrine cell network. J Neurosci 2012; 32:6747-59. [PMID: 22593045 PMCID: PMC3367513 DOI: 10.1523/jneurosci.5087-11.2012] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 02/28/2012] [Accepted: 03/19/2012] [Indexed: 11/21/2022] Open
Abstract
Many neurons are coupled by electrical synapses into networks that have emergent properties. In the retina, coupling in these networks is dynamically regulated by changes in background illumination, optimizing signal integration for the visual environment. However, the mechanisms that control this plasticity are poorly understood. We have investigated these mechanisms in the rabbit AII amacrine cell, a multifunctional retinal neuron that forms an electrically coupled network via connexin 36 (Cx36) gap junctions. We find that presynaptic activity of glutamatergic ON bipolar cells drives increased phosphorylation of Cx36, indicative of increased coupling in the AII network. The phosphorylation is dependent on activation of nonsynaptic NMDA receptors that colocalize with Cx36 on AII amacrine cells, and is mediated by CaMKII. This activity-dependent increase in Cx36 phosphorylation works in opposition to dopamine-driven reduction of phosphorylation, establishing a local dynamic regulatory mechanism, and accounting for the nonlinear control of AII coupling by background illumination.
Collapse
Affiliation(s)
- W Wade Kothmann
- Richard S. Ruiz Department of Ophthalmology and Visual Science, University of Texas Medical School, Houston, Texas 77030, USA.
| | | | | | | | | | | |
Collapse
|
39
|
Hazra A, Rosenbaum R, Bodmann B, Cao S, Josić K, Žiburkus J. β-Adrenergic modulation of spontaneous spatiotemporal activity patterns and synchrony in hyperexcitable hippocampal circuits. J Neurophysiol 2012; 108:658-71. [PMID: 22496530 DOI: 10.1152/jn.00708.2011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
A description of healthy and pathological brain dynamics requires an understanding of spatiotemporal patterns of neural activity and characteristics of its propagation between interconnected circuits. However, the structure and modulation of the neural activation maps underlying these patterns and their propagation remain elusive. We investigated effects of β-adrenergic receptor (β-AR) stimulation on the spatiotemporal characteristics of emergent activity in rat hippocampal circuits. Synchronized epileptiform-like activity, such as interictal bursts (IBs) and ictal-like events (ILEs), were evoked by 4-aminopyridine (4-AP), and their dynamics were studied using a combination of electrophysiology and fast voltage-sensitive dye imaging. Dynamic characterization of the spontaneous IBs showed that they originated in dentate gyrus/CA3 border and propagated toward CA1. To determine how β-AR modulates spatiotemporal characteristics of the emergent IBs, we used the β-AR agonist isoproterenol (ISO). ISO significantly reduced the spatiotemporal extent and propagation velocity of the IBs and significantly altered network activity in the 1- to 20-Hz range. Dual whole cell recordings of the IBs in CA3/CA1 pyramidal cells and optical analysis of those regions showed that ISO application reduced interpyramidal and interregional synchrony during the IBs. In addition, ISO significantly reduced duration not only of the shorter duration IBs but also the prolonged ILEs in 4-AP. To test whether the decrease in ILE duration was model dependent, we used a different hyperexcitability model, zero magnesium (0 Mg(2+)). Prolonged ILEs were readily formed in 0 Mg(2+), and addition of ISO significantly reduced their durations. Taken together, these novel results provide evidence that β-AR activation dynamically reshapes the spatiotemporal activity patterns in hyperexcitable circuits by altering network rhythmogenesis, propagation velocity, and intercellular/regional synchronization.
Collapse
Affiliation(s)
- Anupam Hazra
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
| | | | | | | | | | | |
Collapse
|
40
|
Whittington MA, Roopun AK, Traub RD, Davies CH. Circuits and brain rhythms in schizophrenia: a wealth of convergent targets. Curr Opin Pharmacol 2012; 11:508-14. [PMID: 21555247 DOI: 10.1016/j.coph.2011.04.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 04/17/2011] [Indexed: 11/26/2022]
Abstract
Few common neurological illnesses trace back to single molecular disturbances. Many disparate putative causes may co-associate with a single disease state. However, uncovering functional, hierarchical networks of underlying mechanisms can provide a framework in which many primary pathologies converge on more complex, single higher level correlates of disease. This article focuses on cognitive deficits associated with schizophrenia to illustrate: a) How non-invasive EEG biomarkers of cognitive function constitute such a 'higher level correlate' of underlying pathologies. b) How derangement of multiple, cell-specific, molecular processes can converge on such EEG-visible, correlates of disrupted cognitive function. This approach suggests that evidence-based design of multi-target therapies may take advantage of hierarchical patterns of convergence to improve both efficacy and selectivity of disease-intervention.
Collapse
Affiliation(s)
- Miles A Whittington
- Institute of Neuroscience, The Medical School, Framlington Place, Newcastle University, Newcastle NE2 4HH, UK.
| | | | | | | |
Collapse
|
41
|
Vivacqua G, Casini A, Vaccaro R, Salvi EP, Pasquali L, Fornai F, Yu S, D’Este L. Spinal cord and parkinsonism: Neuromorphological evidences in humans and experimental studies. J Chem Neuroanat 2011; 42:327-40. [DOI: 10.1016/j.jchemneu.2011.03.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 02/20/2011] [Accepted: 03/01/2011] [Indexed: 12/12/2022]
|
42
|
Affiliation(s)
- Shaul Hestrin
- Department of Comparative Medicine, Stanford University, Stanford, CA 94305, USA.
| |
Collapse
|
43
|
Armstrong C, Szabadics J, Tamás G, Soltesz I. Neurogliaform cells in the molecular layer of the dentate gyrus as feed-forward γ-aminobutyric acidergic modulators of entorhinal-hippocampal interplay. J Comp Neurol 2011; 519:1476-91. [PMID: 21452204 DOI: 10.1002/cne.22577] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Feed-forward inhibition from molecular layer interneurons onto granule cells (GCs) in the dentate gyrus is thought to have major effects regulating entorhinal-hippocampal interactions, but the precise identity, properties, and functional connectivity of the GABAergic cells in the molecular layer are not well understood. We used single and paired intracellular patch clamp recordings from post-hoc-identified cells in acute rat hippocampal slices and identified a subpopulation of molecular layer interneurons that expressed immunocytochemical markers present in members of the neurogliaform cell (NGFC) class. Single NGFCs displayed small dendritic trees, and their characteristically dense axonal arborizations covered significant portions of the outer and middle one-thirds of the molecular layer, with frequent axonal projections across the fissure into the CA1 and subicular regions. Typical NGFCs exhibited a late firing pattern with a ramp in membrane potential prior to firing action potentials, and single spikes in NGFCs evoked biphasic, prolonged GABA(A) and GABA(B) postsynaptic responses in GCs. In addition to providing dendritic GABAergic inputs to GCs, NGFCs also formed chemical synapses and gap junctions with various molecular layer interneurons, including other NGFCs. NGFCs received low-frequency spontaneous synaptic events, and stimulation of perforant path fibers revealed direct, facilitating synaptic inputs from the entorhinal cortex. Taken together, these results indicate that NGFCs form an integral part of the local molecular layer microcircuitry generating feed-forward inhibition and provide a direct GABAergic pathway linking the dentate gyrus to the CA1 and subicular regions through the hippocampal fissure.
Collapse
Affiliation(s)
- Caren Armstrong
- Department of Anatomy and Neurobiology, University of California, Irvine, School of Medicine, Irvine, California 92697, USA.
| | | | | | | |
Collapse
|
44
|
Jacobson GM, Voss LJ, Melin SM, Cursons RTM, Sleigh JW. The role of connexin36 gap junctions in modulating the hypnotic effects of isoflurane and propofol in mice. Anaesthesia 2011; 66:361-7. [PMID: 21418043 DOI: 10.1111/j.1365-2044.2011.06658.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Gap junction blockade is a possible mechanism by which general anaesthetic drugs cause unconsciousness. We measured the sensitivity of connexin36 knockout mice to the hypnotic effects of isoflurane and propofol. The experimental endpoint was recovery of the righting reflex of the anaesthetised animals during 0.2% step-reductions in isoflurane concentration, or following intraperitoneal injection of propofol (100 mg.kg(-1) ). Connexin36 knockout animals were more sensitive to the hypnotic effects of isoflurane than 'normal' wild-type animals. The half maximal effective concentration (EC50) for recovery of righting reflex was 0.37% for connexin36 knockout vs 0.49% for wild-type animals (p < 0.001). For propofol, connnexin36 knockout animals showed more rapid loss of righting reflex than wild-type animals (mean (SD) 2.8 (0.13) vs 3.8 (0.27) min); and young (< 60 days) connexin36 knockout animals remained anaesthetised for longer than young wild-type mice (47.2 (2.9) vs 30.5 (1.7) min; p < 0.00001). These findings suggest that the hypnotic effects of anaesthetic drugs may be moderately enhanced by gap junction blockade.
Collapse
Affiliation(s)
- G M Jacobson
- Department of Biological Sciences, Faculty of Science and Engineering, The University of Waikato, Hamilton, New Zealand.
| | | | | | | | | |
Collapse
|
45
|
Connor SA, Hoeffer CA, Klann E, Nguyen PV. Fragile X mental retardation protein regulates heterosynaptic plasticity in the hippocampus. Learn Mem 2011; 18:207-20. [PMID: 21430043 PMCID: PMC3072772 DOI: 10.1101/lm.2043811] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Accepted: 12/28/2010] [Indexed: 01/20/2023]
Abstract
Silencing of a single gene, FMR1, is linked to a highly prevalent form of mental retardation, characterized by social and cognitive impairments, known as fragile X syndrome (FXS). The FMR1 gene encodes fragile X mental retardation protein (FMRP), which negatively regulates translation. Knockout of Fmr1 in mice results in enhanced long-term depression (LTD) induced by metabotropic glutamate receptor (mGluR) activation. Despite the evidence implicating FMRP in LTD, the role of FMRP in long-term potentiation (LTP) is less clear. Synaptic strength can be augmented heterosynaptically through the generation and sequestration of plasticity-related proteins, in a cell-wide manner. If heterosynaptic plasticity is altered in Fmr1 knockout (KO) mice, this may explain the cognitive deficits associated with FXS. We induced homosynaptic plasticity using the β-adrenergic receptor (β-AR) agonist, isoproterenol (ISO), which facilitated heterosynaptic LTP that was enhanced in Fmr1 KO mice relative to wild-type (WT) controls. To determine if enhanced heterosynaptic LTP in Fmr1 KO mouse hippocampus requires protein synthesis, we applied a translation inhibitor, emetine (EME). EME blocked homo- and heterosynaptic LTP in both genotypes. We also probed the roles of mTOR and ERK in boosting heterosynaptic LTP in Fmr1 KO mice. Although heterosynaptic LTP was blocked in both WT and KOs by inhibitors of mTOR and ERK, homosynaptic LTP was still enhanced following mTOR inhibition in slices from Fmr1 KO mice. Because mTOR will normally stimulate translation initiation, our results suggest that β-AR stimulation paired with derepression of translation results in enhanced heterosynaptic plasticity.
Collapse
Affiliation(s)
- Steven A. Connor
- Centre for Neuroscience, University of Alberta School of Medicine, Edmonton AB, T6G 2H7, Canada
| | - Charles A. Hoeffer
- Smilow Neuroscience Program, New York University School of Medicine, New York, New York 10016, USA
| | - Eric Klann
- Center for Neural Science, New York University, New York, New York 10003, USA
| | - Peter V. Nguyen
- Centre for Neuroscience, University of Alberta School of Medicine, Edmonton AB, T6G 2H7, Canada
- Department of Physiology, University of Alberta School of Medicine, Edmonton AB, T6G 2H7, Canada
- Department of Psychiatry, University of Alberta School of Medicine, Edmonton AB, T6G 2H7, Canada
| |
Collapse
|
46
|
Hoge GJ, Davidson KGV, Yasumura T, Castillo PE, Rash JE, Pereda AE. The extent and strength of electrical coupling between inferior olivary neurons is heterogeneous. J Neurophysiol 2010; 105:1089-101. [PMID: 21177999 DOI: 10.1152/jn.00789.2010] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Gap junctions constitute the only form of synaptic communication between neurons in the inferior olive (IO), which gives rise to the climbing fibers innervating the cerebellar cortex. Although its exact functional role remains undetermined, electrical coupling was shown to be necessary for the transient formation of functional compartments of IO neurons and to underlie the precise timing of climbing fibers required for cerebellar learning. So far, most functional considerations assume the existence of a network of permanently and homogeneously coupled IO neurons. Contrasting this notion, our results indicate that coupling within the IO is highly variable. By combining tracer-coupling analysis and paired electrophysiological recordings, we found that individual IO neurons could be coupled to a highly variable number of neighboring neurons. Furthermore, a given neuron could be coupled at remarkably different strengths with each of its partners. Freeze-fracture analysis of IO glomeruli revealed the close proximity of glutamatergic postsynaptic densities to connexin 36-containing gap junctions, at distances comparable to separations between chemical transmitting domains and gap junctions in goldfish mixed contacts, where electrical coupling was shown to be modulated by the activity of glutamatergic synapses. On the basis of structural and molecular similarities with goldfish mixed synapses, we speculate that, rather than being hardwired, variations in coupling could result from glomerulus-specific long-term modulation of gap junctions. This striking heterogeneity of coupling might act to finely influence the synchronization of IO neurons, adding an unexpected degree of complexity to olivary networks.
Collapse
Affiliation(s)
- Gregory J Hoge
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
| | | | | | | | | | | |
Collapse
|
47
|
Abstract
Although the rigorous anatomical definition of the microcircuitry of the brain is essential for understanding its functions, the modulation of the physiological properties of neurons and synapses may confer an additional level of complexity. Here, I review two examples of neuromodulation within a specific microcircuit of the hippocampus, i.e. the local network of stratum lacunosum-moleculare. In particular, I will examine the actions of two different types of neuromodulators on the excitability and electrical coupling of two specific classes of cells. First, I will review the effects of noradrenaline on GABAergic networks. Particular emphasis will be placed on neurogliaform cells. Then, I will describe the chemokinergic modulation of spontaneous firing of Cajal-Retzius cells, mediated by the chemokine (C-X-C motif) ligand 12/stromal cell-derived factor-1 α (CXCL12/SDF-1) via the CXC chemokine receptor 4 (CXCR4). The complexities created by these diverse types of modulations for network activity, together with their potential implications for stratum lacunosum-moleculare processing of information in vivo, will be also presented and briefly discussed.
Collapse
Affiliation(s)
- Gianmaria Maccaferri
- Department of Physiology, Feinberg School of Medicine, Northwestern University Medical School, Chicago, IL 60611, USA.
| |
Collapse
|
48
|
β2 Adrenoreceptor-Mediated Noradrenergic Effect on GABA-ergic Transmission in the CA1 Zone of the Rat Hippocampus in vitro. NEUROPHYSIOLOGY+ 2010. [DOI: 10.1007/s11062-010-9146-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
|
49
|
Helbig I, Sammler E, Eliava M, Bolshakov AP, Rozov A, Bruzzone R, Monyer H, Hormuzdi SG. In vivo evidence for the involvement of the carboxy terminal domain in assembling connexin 36 at the electrical synapse. Mol Cell Neurosci 2010; 45:47-58. [PMID: 20510366 PMCID: PMC3025355 DOI: 10.1016/j.mcn.2010.05.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 05/03/2010] [Accepted: 05/15/2010] [Indexed: 12/03/2022] Open
Abstract
Connexin 36 (Cx36)-containing electrical synapses contribute to the timing and amplitude of neural responses in many brain regions. A Cx36-EGFP transgenic was previously generated to facilitate their identification and study. In this study we demonstrate that electrical coupling is normal in transgenic mice expressing Cx36 from the genomic locus and suggest that fluorescent puncta present in brain tissue represent distributed electrical synapses. These qualities emphasize the usefulness of the Cx36-EGFP reporter as a tool for the detailed anatomical characterization of electrical synapses in fixed and living tissue. However, though the fusion protein is able to form gap junctions between Xenopus laevis oocytes it is unable to restore electrical coupling to interneurons in the Cx36-deficient mouse. Further experiments in transgenic tissue and non-neural cell lines reveal impaired transport to the plasma membrane as the possible cause. By analyzing the functional deficits exhibited by the fusion protein in vivo and in vitro, we identify a motif within Cx36 that may interact with other trafficking or scaffold proteins and thereby be responsible for its incorporation into electrical synapses.
Collapse
Affiliation(s)
- Ingo Helbig
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein (UKSH), Schwanenweg 20, 24105 Kiel, Germany
| | - Esther Sammler
- Centre for Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK
| | - Marina Eliava
- Department of Clinical Neurobiology, University of Heidelberg, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Alexey P. Bolshakov
- Centre for Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK
| | - Andrei Rozov
- Centre for Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK
| | - Roberto Bruzzone
- HKU-Pasteur Research Centre, 1/F, Dexter HC Man Building, Pokfulam, Hong Kong
| | - Hannah Monyer
- Department of Clinical Neurobiology, University of Heidelberg, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Sheriar Gustad Hormuzdi
- Centre for Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK
| |
Collapse
|
50
|
Liu JX, Tang YC, Liu Y, Tang FR. Status epilepticus alters hippocampal PKAbeta and PKAgamma expression in mice. Seizure 2010; 19:414-20. [PMID: 20630779 DOI: 10.1016/j.seizure.2010.06.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 06/12/2010] [Accepted: 06/17/2010] [Indexed: 10/19/2022] Open
Abstract
OBJECTIVES To investigate the localization and progressive changes of cyclic-AMP dependent protein kinase (cPKA) in the mouse hippocampus at acute stages during and after pilocarpine induced status epilepticus. METHODS Pilocarpine induced status epilepticus mice were sacrificed 30 min, 2 h or 1 day after the start of a approximately 7 h lasting status as assessed by video-electroencephalography. Brains were processed for quantitative immunohistochemistry of hippocampal cPKAbeta and cPKAgamma, and immunohistochemical co-localization of cPKAbeta and cPKAgamma with calbindin (CB), calretinin (CR), and parvalbumin (PV). RESULTS Based on anatomical and morphological assessment, cPKAbeta was primarily expressed by principal cells and cPKAgamma by interneurons. In CA1, cPKAbeta co-localized with 76% of CB, 41% of CR, and 95% of PV-immunopositive cells, while cPKAgamma co-localized with 50% of CB, 29% of CR, and 80% of PV-immunopositive cells. Upon induction of status epilepticus, cPKAbeta expression was transiently reduced in CA1, whereas cPKAgamma expression was sustainably reduced. CONCLUSION cPKA may play an important role in neuronal hyperexcitability, death and epileptogenesis during and after pilocarpine induced status epilepticus.
Collapse
Affiliation(s)
- Jian Xin Liu
- Institute of Neurobiology, School of Medicine, Xi'an Jiaotong University, Xi'an, PR China
| | | | | | | |
Collapse
|