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Liddell JR, Hilton JBW, Wang YJ, Billings JL, Nikseresht S, Kysenius K, Fuller-Jackson JP, Hare DJ, Crouch PJ. Decreased spinal cord motor neuron numbers in mice depleted of central nervous system copper. Metallomics 2024; 16:mfae036. [PMID: 39251386 DOI: 10.1093/mtomcs/mfae036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Accepted: 08/03/2024] [Indexed: 09/11/2024]
Abstract
Disrupted copper availability in the central nervous system (CNS) is implicated as a significant feature of the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Solute carrier family 31 member 1 (Slc31a1; Ctr1) governs copper uptake in mammalian cells and mutations affecting Slc31a1 are associated with severe neurological abnormalities. Here, we examined the impact of decreased CNS copper caused by ubiquitous heterozygosity for functional Slc31a1 on spinal cord motor neurons in Slc31a1+/- mice. Congruent with the CNS being relatively susceptible to disrupted copper availability, brain and spinal cord tissue from Slc31a1+/- mice contained significantly less copper than wild-type littermates, even though copper levels in other tissues were unaffected. Slc31a1+/- mice had less spinal cord α-motor neurons compared to wild-type littermates, but they did not develop any overt physical signs of motor impairment. By contrast, ALS model SOD1G37R mice had fewer α-motor neurons than control mice and exhibited clear signs of motor function impairment. With the expression of Slc31a1 notwithstanding, spinal cord expression of genes related to copper handling revealed only minor differences between Slc31a1+/- and wild-type mice. This contrasted with SOD1G37R mice where changes in the expression of copper handling genes were pronounced. Similarly, the expression of genes related to toxic glial activation was unchanged in spinal cords from Slc31a1+/- mice but highly upregulated in SOD1G37R mice. Together, results from the Slc31a1+/- mice and SOD1G37R mice indicate that although depleted CNS copper has a significant impact on spinal cord motor neuron numbers, the manifestation of overt ALS-like motor impairment requires additional factors.
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Affiliation(s)
- J R Liddell
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - J B W Hilton
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Y J Wang
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - J L Billings
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - S Nikseresht
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - K Kysenius
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - J P Fuller-Jackson
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - D J Hare
- Atomic Medicine Initiative, University of Technology Sydney, Sydney, NSW 2007, Australia
| | - P J Crouch
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
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2
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Goncalves MB, Wu Y, Clarke E, Grist J, Moehlin J, Mendoza-Parra MA, Hobbs C, Kalindjian B, Fok H, Mander AP, Hassanin H, Bendel D, Täubel J, Mant T, Carlstedt T, Jack J, Corcoran JPT. C286, an orally available retinoic acid receptor β agonist drug, regulates multiple pathways to achieve spinal cord injury repair. Front Mol Neurosci 2024; 17:1411384. [PMID: 39228795 PMCID: PMC11368863 DOI: 10.3389/fnmol.2024.1411384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Accepted: 07/29/2024] [Indexed: 09/05/2024] Open
Abstract
Retinoic acid receptor β2 (RARβ2) is an emerging therapeutic target for spinal cord injuries (SCIs) with a unique multimodal regenerative effect. We have developed a first-in-class RARβ agonist drug, C286, that modulates neuron-glial pathways to induce functional recovery in a rodent model of sensory root avulsion. Here, using genome-wide and pathway enrichment analysis of avulsed rats' spinal cords, we show that C286 also influences the extracellular milieu (ECM). Protein expression studies showed that C286 upregulates tenascin-C, integrin-α9, and osteopontin in the injured cord. Similarly, C286 remodulates these ECM molecules, hampers inflammation and prevents tissue loss in a rodent model of spinal cord contusion C286. We further demonstrate C286's efficacy in human iPSC-derived neurons, with treatment resulting in a significant increase in neurite outgrowth. Additionally, we identify a putative efficacy biomarker, S100B, which plasma levels correlated with axonal regeneration in nerve-injured rats. We also found that other clinically available retinoids, that are not RARβ specific agonists, did not lead to functional recovery in avulsed rats, demonstrating the requirement for RARβ specific pathways in regeneration. In a Phase 1 trial, the single ascending dose (SAD) cohorts showed increases in expression of RARβ2 in white blood cells correlative to increased doses and at the highest dose administered, the pharmacokinetics were similar to the rat proof of concept (POC) studies. Collectively, our data suggests that C286 signalling in neurite/axonal outgrowth is conserved between species and across nerve injuries. This warrants further clinical testing of C286 to ascertain POC in a broad spectrum of neurodegenerative conditions.
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Affiliation(s)
- Maria B. Goncalves
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
| | - Yue Wu
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
| | - Earl Clarke
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
| | - John Grist
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
| | - Julien Moehlin
- UMR 8030 Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, University of Évry-val-d'Essonne, University Paris-Saclay, Évry, France
| | - Marco Antonio Mendoza-Parra
- UMR 8030 Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, University of Évry-val-d'Essonne, University Paris-Saclay, Évry, France
| | - Carl Hobbs
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
| | - Barret Kalindjian
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
| | - Henry Fok
- NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, United Kingdom
| | - Adrian P. Mander
- Centre for Trials Research, Cardiff University, Cardiff, United Kingdom
| | - Hana Hassanin
- Surrey Clinical Research Centre, University of Surrey, Guildford, United Kingdom
| | - Daryl Bendel
- Surrey Clinical Research Centre, University of Surrey, Guildford, United Kingdom
| | - Jörg Täubel
- Richmond Pharmacology Limited, London, United Kingdom
| | - Tim Mant
- NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, United Kingdom
| | - Thomas Carlstedt
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
| | - Julian Jack
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
| | - Jonathan P. T. Corcoran
- Neuroscience Drug Discovery Unit, Wolfson Sensory, Pain and Regeneration Centre, King's College London, Guy's Campus, London, United Kingdom
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3
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Smith CC, Nascimento F, Özyurt MG, Beato M, Brownstone RM. Kv2 channels do not function as canonical delayed rectifiers in spinal motoneurons. iScience 2024; 27:110444. [PMID: 39148717 PMCID: PMC11325356 DOI: 10.1016/j.isci.2024.110444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/29/2024] [Accepted: 07/01/2024] [Indexed: 08/17/2024] Open
Abstract
The increased muscular force output required for some behaviors is achieved via amplification of motoneuron output via cholinergic C-bouton synapses. Work in neonatal mouse motoneurons suggested that modulation of currents mediated by post-synaptically clustered KV2.1 channels is crucial to C-bouton amplification. By focusing on more mature motoneurons, we show that conditional knockout of KV2.1 channels minimally affects either excitability or response to exogenously applied muscarine. Similarly, unlike in neonatal motoneurons or cortical pyramidal neurons, pharmacological blockade of KV2 currents has minimal effect on mature motoneuron firing in vitro. Furthermore, in vivo amplification of electromyography activity and high-force task performance was unchanged following KV2.1 knockout. Finally, we show that KV2.2 is also expressed by spinal motoneurons, colocalizing with KV2.1 opposite C-boutons. We suggest that the primary function of KV2 proteins in motoneurons is non-conducting and that KV2.2 can function in this role in the absence of KV2.1.
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Affiliation(s)
- Calvin C Smith
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Filipe Nascimento
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - M Görkem Özyurt
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Marco Beato
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK
| | - Robert M Brownstone
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
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4
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Goffin L, Lemoine D, Clotman F. Potential contribution of spinal interneurons to the etiopathogenesis of amyotrophic lateral sclerosis. Front Neurosci 2024; 18:1434404. [PMID: 39091344 PMCID: PMC11293063 DOI: 10.3389/fnins.2024.1434404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Accepted: 06/21/2024] [Indexed: 08/04/2024] Open
Abstract
Amyotrophic lateral sclerosis (ALS) consists of a group of adult-onset fatal and incurable neurodegenerative disorders characterized by the progressive death of motor neurons (MNs) throughout the central nervous system (CNS). At first, ALS was considered to be an MN disease, caused by cell-autonomous mechanisms acting specifically in MNs. Accordingly, data from ALS patients and ALS animal models revealed alterations in excitability in multiple neuronal populations, including MNs, which were associated with a variety of cellular perturbations such as protein aggregation, ribonucleic acid (RNA) metabolism defects, calcium dyshomeostasis, modified electrophysiological properties, and autophagy malfunctions. However, experimental evidence rapidly demonstrated the involvement of other types of cells, including glial cells, in the etiopathogenesis of ALS through non-cell autonomous mechanisms. Surprisingly, the contribution of pre-motor interneurons (INs), which regulate MN activity and could therefore critically modulate their excitability at the onset or during the progression of the disease, has to date been severely underestimated. In this article, we review in detail how spinal pre-motor INs are affected in ALS and their possible involvement in the etiopathogenesis of the disease.
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Affiliation(s)
| | | | - Frédéric Clotman
- Université catholique de Louvain, Louvain Institute of Biomolecular Science and Technology, Animal Molecular and Cellular Biology, Louvain-la-Neuve, Belgium
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5
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Montañana-Rosell R, Selvan R, Hernández-Varas P, Kaminski JM, Sidhu SK, Ahlmark DB, Kiehn O, Allodi I. Spinal inhibitory neurons degenerate before motor neurons and excitatory neurons in a mouse model of ALS. SCIENCE ADVANCES 2024; 10:eadk3229. [PMID: 38820149 PMCID: PMC11141618 DOI: 10.1126/sciadv.adk3229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 04/29/2024] [Indexed: 06/02/2024]
Abstract
Amyotrophic lateral sclerosis (ALS) is characterized by the progressive loss of somatic motor neurons. A major focus has been directed to motor neuron intrinsic properties as a cause for degeneration, while less attention has been given to the contribution of spinal interneurons. In the present work, we applied multiplexing detection of transcripts and machine learning-based image analysis to investigate the fate of multiple spinal interneuron populations during ALS progression in the SOD1G93A mouse model. The analysis showed that spinal inhibitory interneurons are affected early in the disease, before motor neuron death, and are characterized by a slow progressive degeneration, while excitatory interneurons are affected later with a steep progression. Moreover, we report differential vulnerability within inhibitory and excitatory subpopulations. Our study reveals a strong interneuron involvement in ALS development with interneuron specific degeneration. These observations point to differential involvement of diverse spinal neuronal circuits that eventually may be determining motor neuron degeneration.
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Affiliation(s)
| | - Raghavendra Selvan
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
- Department of Computer Science, University of Copenhagen, Copenhagen, Denmark
| | - Pablo Hernández-Varas
- Core Facility for Integrated Microscopy, University of Copenhagen, Copenhagen, Denmark
| | - Jan M. Kaminski
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
- Department of Computer Science, University of Copenhagen, Copenhagen, Denmark
| | | | - Dana B. Ahlmark
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Ole Kiehn
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Ilary Allodi
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK
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6
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Antonucci S, Caron G, Dikwella N, Krishnamurty SS, Harster A, Zarrin H, Tahanis A, Heuvel FO, Danner SM, Ludolph A, Grycz K, Baczyk M, Zytnicki D, Roselli F. Non-canonical adrenergic neuromodulation of motoneuron intrinsic excitability through β-receptors in wild-type and ALS mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.25.586570. [PMID: 38585891 PMCID: PMC10996613 DOI: 10.1101/2024.03.25.586570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Altered neuronal excitability and synaptic inputs to motoneurons are part of the pathophysiology of Amyotrophic Lateral Sclerosis. The cAMP/PKA pathway regulates both of them but therapeutic interventions at this level are limited by the lack of knowledge about suitable pharmacological entry points. Here we used transcriptomics on microdissected and in situ motoneurons to reveal the modulation of PKA-coupled receptorome in SOD1(G93A) ALS mice, vs WT, demonstrating the dysregulation of multiple PKA-coupled GPCRs, in particular on vulnerable MNs, and the relative sparing of β-adrenergic receptors. In vivo MN electrophysiology showed that β2/β3 agonists acutely increase excitability, in particular the input/output relationship, demonstrating a non-canonical adrenergic neuromodulation mediated by β2/β3 receptors both in WT and SOD1 mice. The excitability increase corresponds to the upregulation of immediate-early gene expression and dysregulation of ion channels transcriptome. However the β2/β3 neuromodulation is submitted to a strong homeostasis, since a ten days delivery of β2/β3 agonists results in an abolition of the excitability increase. The homeostatic response is largely caused by a substantial downregulation of PKA-coupled GPCRs in MNs from WT and SOD1 mice. Thus, β-adrenergic receptors are physiologically involved in the regulation of MN excitability and transcriptomics, but, intriguingly, a strong homeostatic response is triggered upon chronic pharmacologic intervention.
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Affiliation(s)
| | - Guillaume Caron
- Université Paris Cité, CNRS, Saints-Pères Paris Institute for the Neurosciences, Paris, France
| | | | | | - Anthony Harster
- Université Paris Cité, CNRS, Saints-Pères Paris Institute for the Neurosciences, Paris, France
| | | | | | | | - Simon M. Danner
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, United States
| | - Albert Ludolph
- Dept. of Neurology, Ulm University, Ulm, DE
- German Center for Neurodegenerative Diseases (DZNE)-Ulm, DE
| | - Kamil Grycz
- Dept. of Neurobiology, Poznan University of Physical Education, Poland
| | - Marcin Baczyk
- Dept. of Neurobiology, Poznan University of Physical Education, Poland
| | - Daniel Zytnicki
- Université Paris Cité, CNRS, Saints-Pères Paris Institute for the Neurosciences, Paris, France
| | - Francesco Roselli
- Dept. of Neurology, Ulm University, Ulm, DE
- German Center for Neurodegenerative Diseases (DZNE)-Ulm, DE
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7
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Sharples SA, Broadhead MJ, Gray JA, Miles GB. M-type potassium currents differentially affect activation of motoneuron subtypes and tune recruitment gain. J Physiol 2023; 601:5751-5775. [PMID: 37988235 DOI: 10.1113/jp285348] [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: 07/27/2023] [Accepted: 10/25/2023] [Indexed: 11/23/2023] Open
Abstract
The size principle is a key mechanism governing the orderly recruitment of motor units and is believed to be dependent on passive properties of the constituent motoneurons. However, motoneurons are endowed with voltage-sensitive ion channels that create non-linearities in their input-output functions. Here we describe a role for the M-type potassium current, conducted by KCNQ channels, in the control of motoneuron recruitment in mice. Motoneurons were studied with whole-cell patch clamp electrophysiology in transverse spinal slices and identified based on delayed (fast) and immediate (slow) onsets of repetitive firing. M-currents were larger in delayed compared to immediate firing motoneurons, which was not reflected by variations in the presence of Kv7.2 or Kv7.3 subunits. Instead, a more depolarized spike threshold in delayed-firing motoneurons afforded a greater proportion of the total M-current to become activated within the subthreshold voltage range, which translated to a greater influence on their recruitment with little influence on their firing rates. Pharmacological activation of M-currents also influenced motoneuron recruitment at the population level, producing a rightward shift in the recruitment curve of monosynaptic reflexes within isolated mouse spinal cords. These results demonstrate a prominent role for M-type potassium currents in regulating the function of motor units, which occurs primarily through the differential control of motoneuron subtype recruitment. More generally, these findings highlight the importance of active properties mediated by voltage-sensitive ion channels in the differential control of motoneuron recruitment, which is a key mechanism for the gradation of muscle force. KEY POINTS: M-currents exert an inhibitory influence on spinal motor output. This inhibitory influence is exerted by controlling the recruitment, but not the firing rate, of high-threshold fast-like motoneurons, with limited influence on low-threshold slow-like motoneurons. Preferential control of fast motoneurons may be linked to a larger M-current that is activated within the subthreshold voltage range compared to slow motoneurons. Larger M-currents in fast compared to slow motoneurons are not accounted for by differences in Kv7.2 or Kv7.3 channel composition. The orderly recruitment of motoneuron subtypes is shaped by differences in the contribution of voltage-gated ion channels, including KCNQ channels. KCNQ channels may provide a target to dynamically modulate the recruitment gain across the motor pool and readily adjust movement vigour.
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Affiliation(s)
- Simon A Sharples
- School of Psychology and Neuroscience, University of St Andrews, Fife, UK
| | | | - James A Gray
- School of Psychology and Neuroscience, University of St Andrews, Fife, UK
| | - Gareth B Miles
- School of Psychology and Neuroscience, University of St Andrews, Fife, UK
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8
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Eleftheriadis PE, Pothakos K, Sharples SA, Apostolou PE, Mina M, Tetringa E, Tsape E, Miles GB, Zagoraiou L. Peptidergic modulation of motor neuron output via CART signaling at C bouton synapses. Proc Natl Acad Sci U S A 2023; 120:e2300348120. [PMID: 37733738 PMCID: PMC10523464 DOI: 10.1073/pnas.2300348120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 07/17/2023] [Indexed: 09/23/2023] Open
Abstract
The intensity of muscle contraction, and therefore movement vigor, needs to be adaptable to enable complex motor behaviors. This can be achieved by adjusting the properties of motor neurons, which form the final common pathway for all motor output from the central nervous system. Here, we identify roles for a neuropeptide, cocaine- and amphetamine-regulated transcript (CART), in the control of movement vigor. We reveal distinct but parallel mechanisms by which CART and acetylcholine, both released at C bouton synapses on motor neurons, selectively amplify the output of subtypes of motor neurons that are recruited during intense movement. We find that mice with broad genetic deletion of CART or selective elimination of acetylcholine from C boutons exhibit deficits in behavioral tasks that require higher levels of motor output. Overall, these data uncover spinal modulatory mechanisms that control movement vigor to support movements that require a high degree of muscle force.
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Affiliation(s)
| | - Konstantinos Pothakos
- Center of Basic Research, Biomedical Research Foundation Academy of Athens, Athens11527, Greece
| | - Simon A. Sharples
- School of Psychology and Neuroscience, University of St. Andrews, St. AndrewsKY16 9JP, United Kingdom
| | - Panagiota E. Apostolou
- Center of Basic Research, Biomedical Research Foundation Academy of Athens, Athens11527, Greece
| | - Maria Mina
- Center of Basic Research, Biomedical Research Foundation Academy of Athens, Athens11527, Greece
| | - Efstathia Tetringa
- Center of Basic Research, Biomedical Research Foundation Academy of Athens, Athens11527, Greece
| | - Eirini Tsape
- Center of Basic Research, Biomedical Research Foundation Academy of Athens, Athens11527, Greece
| | - Gareth B. Miles
- School of Psychology and Neuroscience, University of St. Andrews, St. AndrewsKY16 9JP, United Kingdom
| | - Laskaro Zagoraiou
- Center of Basic Research, Biomedical Research Foundation Academy of Athens, Athens11527, Greece
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9
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Singhal P, Senecal JMM, Senecal JEM, Silwal P, Lynn BD, Nagy JI. Characteristics of Electrical Synapses, C-terminals and Small-conductance Ca 2+ activated Potassium Channels in the Sexually Dimorphic Cremaster Motor Nucleus in Spinal Cord of Mouse and Rat. Neuroscience 2023; 521:58-76. [PMID: 37100373 DOI: 10.1016/j.neuroscience.2023.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 03/17/2023] [Accepted: 04/18/2023] [Indexed: 04/28/2023]
Abstract
Sexually dimorphic motoneurons (MNs) located in lower lumbar spinal cord are involved in mating and reproductive behaviours and are known to be coupled by electrical synapses. The cremaster motor nucleus in upper lumbar spinal cord has also been suggested to support physiological processes associated with sexual behaviours in addition to its thermoregulatory and protective role in maintaining testes integrity. Using immunofluorescence approaches, we investigated whether cremaster MNs also exhibit features reflecting their potential for electrical synaptic communication and examined some of their other synaptic characteristics. Both mice and rats displayed punctate immunolabelling of Cx36 associated with cremaster MNs, indicative of gap junction formation. Transgenic mice with enhanced green fluorescent protein (eGFP) reporter for connexin36 expression showed that subpopulations of cremaster MNs in both male and female mice express eGFP, with greater proportions of those in male mice. The eGFP+ MNs within the cremaster nucleus vs. eGFP- MNs inside and outside this nucleus displayed a 5-fold greater density of serotonergic innervation and exhibited a paucity of innervation by C-terminals arising from cholinergic V0c interneurons. All MNs within the cremaster motor nucleus displayed prominent patches of immunolabelling for SK3 (K+) channels around their periphery, suggestive of their identity as slow MNs, many though not all of which were in apposition to C-terminals. The results provide evidence for electrical coupling of a large proportion of cremaster MNs and suggest the existence of two populations of these MNs with possibly differential innervation of their peripheral target muscles serving different functions.
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Affiliation(s)
- P Singhal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - J M M Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - J E M Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - P Silwal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - B D Lynn
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - J I Nagy
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada.
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10
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Mille T, Bonilla A, Guillaud E, Bertrand SS, Menuet C, Cazalets JR. Muscarinic cholinergic modulation of cardiovascular variables in spinal cord injured rats. Exp Neurol 2023; 363:114369. [PMID: 36878399 DOI: 10.1016/j.expneurol.2023.114369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 02/16/2023] [Accepted: 02/28/2023] [Indexed: 03/07/2023]
Abstract
Spinal cord injury (SCI) leads not only to major impairments in sensorimotor control but also to dramatic dysregulation of autonomic functions including major cardiovascular disturbances. Consequently, individuals with SCI endure daily episodic hypo/hypertension and are at increased risk for cardiovascular disease. Several studies have suggested that an intrinsic spinal coupling mechanism between motor and sympathetic neuronal networks exist and that propriospinal cholinergic neurons may be responsible for a synchronized activation of both somatic and sympathetic outputs. We therefore investigated in the present study, the effect of cholinergic muscarinic agonists on cardiovascular parameters in freely moving adult rats after SCI. Female Sprague-Dawley rats were implanted with radiotelemetry sensors for long-term in vivo monitoring of blood pressure (BP). From BP signal, we calculated heart rate (HR) and respiratory frequency. We first characterized the physiological changes occurring after a SCI performed at the T3-T4 level in our experimental model system. We then investigated the effects on BP, HR and respiration, of the muscarinic agonist oxotremorine using one variant that crossed the blood brain barrier (Oxo-S) and one that does not (Oxo-M) in both Pre- and Post-SCI animals. After SCI, both HR and respiratory frequency increased. BP values exhibited an immediate profound drop before progressively increasing over the three-week post-lesion period but remained below control values. A spectral analysis of BP signal revealed the disappearance of the low frequency component of BP (0.3-0.6 Hz) referred to as Mayer waves after SCI. In Post-SCI animals, central effects mediated by Oxo-S led to an increase in HR and MAP, a slowdown in respiratory frequency and to an increased power in the 0.3-0.6 Hz frequency band. This study unravels some of the mechanisms by which muscarinic activation of spinal neurons could contribute to partial restoration of BP after SCI.
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Affiliation(s)
- Théo Mille
- Université de Bordeaux, CNRS UMR 5287, INCIA, Zone nord, Bat 2, 2e étage, 146 rue Léo Saignat, 33076 Bordeaux cedex, France
| | - Aurélie Bonilla
- Université de Bordeaux, CNRS UMR 5287, INCIA, Zone nord, Bat 2, 2e étage, 146 rue Léo Saignat, 33076 Bordeaux cedex, France
| | - Etienne Guillaud
- Université de Bordeaux, CNRS UMR 5287, INCIA, Zone nord, Bat 2, 2e étage, 146 rue Léo Saignat, 33076 Bordeaux cedex, France
| | - Sandrine S Bertrand
- Université de Bordeaux, CNRS UMR 5287, INCIA, Zone nord, Bat 2, 2e étage, 146 rue Léo Saignat, 33076 Bordeaux cedex, France
| | - Clément Menuet
- Institut de Neurobiologie de la Méditerranée, INMED UMR 1249, INSERM, Aix-Marseille Université, Marseille, France
| | - Jean-René Cazalets
- Université de Bordeaux, CNRS UMR 5287, INCIA, Zone nord, Bat 2, 2e étage, 146 rue Léo Saignat, 33076 Bordeaux cedex, France.
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11
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Wilson AC, Sweeney LB. Spinal cords: Symphonies of interneurons across species. Front Neural Circuits 2023; 17:1146449. [PMID: 37180760 PMCID: PMC10169611 DOI: 10.3389/fncir.2023.1146449] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 03/23/2023] [Indexed: 05/16/2023] Open
Abstract
Vertebrate movement is orchestrated by spinal inter- and motor neurons that, together with sensory and cognitive input, produce dynamic motor behaviors. These behaviors vary from the simple undulatory swimming of fish and larval aquatic species to the highly coordinated running, reaching and grasping of mice, humans and other mammals. This variation raises the fundamental question of how spinal circuits have changed in register with motor behavior. In simple, undulatory fish, exemplified by the lamprey, two broad classes of interneurons shape motor neuron output: ipsilateral-projecting excitatory neurons, and commissural-projecting inhibitory neurons. An additional class of ipsilateral inhibitory neurons is required to generate escape swim behavior in larval zebrafish and tadpoles. In limbed vertebrates, a more complex spinal neuron composition is observed. In this review, we provide evidence that movement elaboration correlates with an increase and specialization of these three basic interneuron types into molecularly, anatomically, and functionally distinct subpopulations. We summarize recent work linking neuron types to movement-pattern generation across fish, amphibians, reptiles, birds and mammals.
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Affiliation(s)
| | - Lora B. Sweeney
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Lower Austria, Austria
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12
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Kong L, Hassinan CW, Gerstner F, Buettner JM, Petigrow JB, Valdivia DO, Chan-Cortés MH, Mistri A, Cao A, McGaugh SA, Denton M, Brown S, Ross J, Schwab MH, Simon CM, Sumner CJ. Boosting neuregulin 1 type-III expression hastens SMA motor axon maturation. Acta Neuropathol Commun 2023; 11:53. [PMID: 36997967 PMCID: PMC10061791 DOI: 10.1186/s40478-023-01551-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 03/12/2023] [Indexed: 04/01/2023] Open
Abstract
Intercellular communication between axons and Schwann cells is critical for attaining the complex morphological steps necessary for axon maturation. In the early onset motor neuron disease spinal muscular atrophy (SMA), many motor axons are not ensheathed by Schwann cells nor grow sufficiently in radial diameter to become myelinated. These developmentally arrested motor axons are dysfunctional and vulnerable to rapid degeneration, limiting efficacy of current SMA therapeutics. We hypothesized that accelerating SMA motor axon maturation would improve their function and reduce disease features. A principle regulator of peripheral axon development is neuregulin 1 type III (NRG1-III). Expressed on axon surfaces, it interacts with Schwann cell receptors to mediate axon ensheathment and myelination. We examined NRG1 mRNA and protein expression levels in human and mouse SMA tissues and observed reduced expression in SMA spinal cord and in ventral, but not dorsal root axons. To determine the impact of neuronal NRG1-III overexpression on SMA motor axon development, we bred NRG1-III overexpressing mice to SMA∆7 mice. Neonatally, elevated NRG1-III expression increased SMA ventral root size as well as axon segregation, diameter, and myelination resulting in improved motor axon conduction velocities. NRG1-III was not able to prevent distal axonal degeneration nor improve axon electrophysiology, motor behavior, or survival of older mice. Together these findings demonstrate that early SMA motor axon developmental impairments can be ameliorated by a molecular strategy independent of SMN replacement providing hope for future SMA combinatorial therapeutic approaches.
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Affiliation(s)
- Lingling Kong
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Cera W Hassinan
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Florian Gerstner
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Jannik M Buettner
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Jeffrey B Petigrow
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - David O Valdivia
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Michelle H Chan-Cortés
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Amy Mistri
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Annie Cao
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Scott Alan McGaugh
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Madeline Denton
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Stephen Brown
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Joshua Ross
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Markus H Schwab
- Department of Neuropathology, University Hospital Leipzig, Leipzig, Germany
| | - Christian M Simon
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Charlotte J Sumner
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA.
- Departments of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
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13
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Bak AN, Djukic S, Kadlecova M, Braunstein TH, Jensen DB, Meehan CF. Cytoplasmic TDP-43 accumulation drives changes in C-bouton number and size in a mouse model of sporadic Amyotrophic Lateral Sclerosis. Mol Cell Neurosci 2023; 125:103840. [PMID: 36921783 DOI: 10.1016/j.mcn.2023.103840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 02/11/2023] [Accepted: 03/04/2023] [Indexed: 03/14/2023] Open
Abstract
An altered neuronal excitability of spinal motoneurones has consistently been implicated in Amyotrophic Lateral Sclerosis (ALS) leading to several investigations of synaptic input to these motoneurones. One such input that has repeatedly been shown to be affected is a population of large cholinergic synapses terminating mainly on the soma of the motoneurones referred to as C-boutons. Most research on these synapses during disease progression has used transgenic Superoxide Dismutase 1 (SOD1) mouse models of the disease which have not only produced conflicting findings, but also fail to recapitulate the key pathological feature seen in ALS; cytoplasmic accumulations of TAR DNA-binding protein 43 (TDP-43). Additionally, they fail to distinguish between slow and fast motoneurones, the latter of which have more C-boutons, but are lost earlier in the disease. To circumvent these issues, we quantified the frequency and volume of C-boutons on traced soleus and gastrocnemius motoneurones, representing predominantly slow and fast motor pools respectively. Experiments were performed using the TDP-43ΔNLS mouse model that carries a transgenic construct of TDP-43 devoid of its nuclear localization signal, preventing its nuclear import. This results in the emergence of pathological TDP-43 inclusions in the cytoplasm, modelling the main pathology seen in this disorder, accompanied by a severe and lethal ALS phenotype. Our results confirmed changes in both the number and volume of C-boutons with a decrease in number on the more vulnerable, predominantly fast gastrocnemius motoneurones and an increase in number on the less vulnerable, predominantly slow soleus motoneurones. Importantly, these changes were only found in male mice. However, both sexes and motor pools showed a decrease in C-bouton volume. Our experiments confirm that cytoplasmic TDP-43 accumulation is sufficient to drive C-bouton changes.
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Affiliation(s)
| | - Svetlana Djukic
- Department of Neuroscience, University of Copenhagen, Denmark
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14
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Nakamura Y, Kurabe M, Matsumoto M, Sato T, Miytashita S, Hoshina K, Kamiya Y, Tainaka K, Matsuzawa H, Ohno N, Ueno M. Cerebrospinal fluid-contacting neuron tracing reveals structural and functional connectivity for locomotion in the mouse spinal cord. eLife 2023; 12:83108. [PMID: 36805807 PMCID: PMC9943067 DOI: 10.7554/elife.83108] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 02/03/2023] [Indexed: 02/22/2023] Open
Abstract
Cerebrospinal fluid-contacting neurons (CSF-cNs) are enigmatic mechano- or chemosensory cells lying along the central canal of the spinal cord. Recent studies in zebrafish larvae and lampreys have shown that CSF-cNs control postures and movements via spinal connections. However, the structures, connectivity, and functions in mammals remain largely unknown. Here we developed a method to genetically target mouse CSF-cNs that highlighted structural connections and functions. We first found that intracerebroventricular injection of adeno-associated virus with a neuron-specific promoter and Pkd2l1-Cre mice specifically labeled CSF-cNs. Single-cell labeling of 71 CSF-cNs revealed rostral axon extensions of over 1800 μm in unmyelinated bundles in the ventral funiculus and terminated on CSF-cNs to form a recurrent circuitry, which was further determined by serial electron microscopy and electrophysiology. CSF-cNs were also found to connect with axial motor neurons and premotor interneurons around the central canal and within the axon bundles. Chemogenetic CSF-cNs inactivation reduced speed and step frequency during treadmill locomotion. Our data revealed the basic structures and connections of mouse CSF-cNs to control spinal motor circuits for proper locomotion. The versatile methods developed in this study will contribute to further understanding of CSF-cN functions in mammals.
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Affiliation(s)
- Yuka Nakamura
- Department of System Pathology for Neurological Disorders, Brain Research Institute, Niigata UniversityNiigataJapan
| | - Miyuki Kurabe
- Division of Anesthesiology, Niigata University Graduate School of Medical and Dental SciencesNiigataJapan
| | - Mami Matsumoto
- Section of Electron Microscopy, Supportive Center for Brain Research, National Institute for Physiological SciencesOkazakiJapan,Department of Developmental and Regenerative Neurobiology, Institute of Brain Science, Nagoya City University Graduate School of Medical SciencesNagoyaJapan
| | - Tokiharu Sato
- Department of System Pathology for Neurological Disorders, Brain Research Institute, Niigata UniversityNiigataJapan
| | - Satoshi Miytashita
- Department of System Pathology for Neurological Disorders, Brain Research Institute, Niigata UniversityNiigataJapan
| | - Kana Hoshina
- Department of System Pathology for Neurological Disorders, Brain Research Institute, Niigata UniversityNiigataJapan
| | - Yoshinori Kamiya
- Division of Anesthesiology, Niigata University Graduate School of Medical and Dental SciencesNiigataJapan
| | - Kazuki Tainaka
- Department of System Pathology for Neurological Disorders, Brain Research Institute, Niigata UniversityNiigataJapan
| | - Hitoshi Matsuzawa
- Center for Advanced Medicine and Clinical Research, Kashiwaba Neurosurgical HospitalSapporoJapan,Center for Integrated Human Brain Science, Niigata UniversityNiigataJapan
| | - Nobuhiko Ohno
- Department of Anatomy, Division of Histology and Cell Biology, Jichi Medical University, School of MedicineShimotsukeJapan,Division of Ultrastructural Research, National Institute for Physiological SciencesOkazakiJapan
| | - Masaki Ueno
- Department of System Pathology for Neurological Disorders, Brain Research Institute, Niigata UniversityNiigataJapan
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15
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Fisher KM, Garner JP, Darian-Smith C. Small sensory spinal lesions that affect hand function in monkeys greatly alter primary afferent and motor neuron connections in the cord. J Comp Neurol 2022; 530:3039-3055. [PMID: 35973735 PMCID: PMC9561953 DOI: 10.1002/cne.25395] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 05/20/2022] [Accepted: 07/15/2022] [Indexed: 11/08/2022]
Abstract
Small sensory spinal injuries induce plasticity across the neuraxis, but little is understood about their effect on segmental connections or motor neuron (MN) function. Here, we begin to address this at two levels. First, we compared afferent input distributions from the skin and muscles of the digits with corresponding MN pools to determine their spatial relationship, in both the normal state and 4-6 months after a unilateral dorsal root/dorsal column lesion (DRL/DCL), affecting digits 1-3. Second, we looked at specific changes to MN inputs and membrane properties that likely impact functional recovery. Monkeys received a targeted unilateral DRL/DCL, and 4-6 months later, cholera toxin subunit B (CT-B) was injected bilaterally into either the distal pads of digits 1-3, or related intrinsic hand muscles, to label inputs to the cord, and corresponding MNs. In controls (unlesioned side), cutaneous and proprioceptive afferents from digits 1-3 showed different distribution patterns but similar rostrocaudal spread within the dorsal horn from C1 to T2. In contrast, MNs were distributed across just two segments (C7-8). Following the lesion, sensory inputs were significantly diminished across all 10 segments, though this did not alter MN distributions. Afferent and monoamine inputs, as well as KCC2 cotransporters, were also significantly altered on the cell membrane of CT-B labeled MNs postlesion. In contrast, inhibitory neurotransmission and perineuronal net integrity were not altered at this prechronic timepoint. Our findings indicate that even a small sensory injury can significantly impact sensory and motor spinal neurons and provide new insight into the complex process of recovery.
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Affiliation(s)
- Karen M. Fisher
- Department of Comparative Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA94305-5342
| | - Joseph P. Garner
- Department of Comparative Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA94305-5342
| | - Corinna Darian-Smith
- Department of Comparative Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA94305-5342
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16
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BDNF Spinal Overexpression after Spinal Cord Injury Partially Protects Soleus Neuromuscular Junction from Disintegration, Increasing VAChT and AChE Transcripts in Soleus but Not Tibialis Anterior Motoneurons. Biomedicines 2022; 10:biomedicines10112851. [DOI: 10.3390/biomedicines10112851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/20/2022] [Accepted: 11/04/2022] [Indexed: 11/09/2022] Open
Abstract
After spinal cord transection (SCT) the interaction between motoneurons (MNs) and muscle is impaired, due to reorganization of the spinal network after a loss of supraspinal inputs. Rats subjected to SCT, treated with intraspinal injection of a AAV-BDNF (brain-derived neurotrophic factor) construct, partially regained the ability to walk. The central effects of this treatment have been identified, but its impact at the neuromuscular junction (NMJ) has not been characterized. Here, we compared the ability of NMJ pre- and postsynaptic machinery in the ankle extensor (Sol) and flexor (TA) muscles to respond to intraspinal AAV-BDNF after SCT. The gene expression of cholinergic molecules (VAChT, ChAT, AChE, nAChR, mAChR) was investigated in tracer-identified, microdissected MN perikarya, and in muscle fibers with the use of qPCR. In the NMJs, a distribution of VAChT, nAChR and Schwann cells was studied by immunofluorescence, and of synaptic vesicles and membrane active zones by electron microscopy. We showed partial protection of the Sol NMJs from disintegration, and upregulation of the VAChT and AChE transcripts in the Sol, but not the TA MNs after spinal enrichment with BDNF. We propose that the observed discrepancy in response to BDNF treatment is an effect of difference in the TrkB expression setting BDNF responsiveness, and of BDNF demands in Sol and TA muscles.
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17
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Spinal Cord Circuits: Models and Reality. NEUROPHYSIOLOGY+ 2022. [DOI: 10.1007/s11062-022-09927-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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18
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Le Ray D, Bertrand SS, Dubuc R. Cholinergic Modulation of Locomotor Circuits in Vertebrates. Int J Mol Sci 2022; 23:ijms231810738. [PMID: 36142651 PMCID: PMC9501616 DOI: 10.3390/ijms231810738] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 09/08/2022] [Accepted: 09/09/2022] [Indexed: 11/24/2022] Open
Abstract
Locomotion is a basic motor act essential for survival. Amongst other things, it allows animals to move in their environment to seek food, escape predators, or seek mates for reproduction. The neural mechanisms involved in the control of locomotion have been examined in many vertebrate species and a clearer picture is progressively emerging. The basic muscle synergies responsible for propulsion are generated by neural networks located in the spinal cord. In turn, descending supraspinal inputs are responsible for starting, maintaining, and stopping locomotion as well as for steering and controlling speed. Several neurotransmitter systems play a crucial role in modulating the neural activity during locomotion. For instance, cholinergic inputs act both at the spinal and supraspinal levels and the underlying mechanisms are the focus of the present review. Much information gained on supraspinal cholinergic modulation of locomotion was obtained from the lamprey model. Nicotinic cholinergic inputs increase the level of excitation of brainstem descending command neurons, the reticulospinal neurons (RSNs), whereas muscarinic inputs activate a select group of hindbrain neurons that project to the RSNs to boost their level of excitation. Muscarinic inputs also reduce the transmission of sensory inputs in the brainstem, a phenomenon that could help in sustaining goal directed locomotion. In the spinal cord, intrinsic cholinergic inputs strongly modulate the activity of interneurons and motoneurons to control the locomotor output. Altogether, the present review underlines the importance of the cholinergic inputs in the modulation of locomotor activity in vertebrates.
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Affiliation(s)
- Didier Le Ray
- Institut des Neurosciences Cognitives et Intégratives d’Aquitaine (INCIA), UMR 5287, Université de Bordeaux-CNRS, F-33076 Bordeaux, France
- Correspondence: (D.L.R.); (R.D.)
| | - Sandrine S. Bertrand
- Institut des Neurosciences Cognitives et Intégratives d’Aquitaine (INCIA), UMR 5287, Université de Bordeaux-CNRS, F-33076 Bordeaux, France
| | - Réjean Dubuc
- Department of Neurosciences, Université de Montréal, Montréal, QC H3C 3J7, Canada
- Department of Physical Activity Sciences and Research Group in Adapted Physical Activity, Université du Québec à Montréal, Montréal, QC H3C 3P8, Canada
- Correspondence: (D.L.R.); (R.D.)
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19
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Niakani S, Liu H, Liu WY, Horner RL. Differential pharmacological and sex-specific effects of antimuscarinic agents at the hypoglossal motor nucleus in vivo in rats. Sci Rep 2022; 12:14896. [PMID: 36050440 PMCID: PMC9437041 DOI: 10.1038/s41598-022-19233-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 08/25/2022] [Indexed: 12/01/2022] Open
Abstract
Successful cholinergic-noradrenergic pharmacotherapy for obstructive sleep apnea (OSA) is thought to be due to effects at the hypoglossal motor nucleus (HMN). Clinical efficacy varies with muscarinic-receptor (MR) subtype affinities. We hypothesized that oxybutynin (cholinergic agent in successful OSA pharmacotherapy) is an effective MR antagonist at the HMN and characterized its efficacy with other antagonists. We recorded tongue muscle activity of isoflurane anesthetized rats (121 males and 60 females, 7-13 per group across 13 protocols) in response to HMN microperfusion with MR antagonists with and without: (i) eserine-induced increased endogenous acetylcholine at the HMN and (ii) muscarine. Eserine-induced increased acetylcholine decreased tongue motor activity (p < 0.001) with lesser cholinergic suppression in females versus males (p = 0.017). Motor suppression was significantly attenuated by the MR antagonists atropine, oxybutynin, and omadacycline (MR2 antagonist), each p < 0.001, with similar residual activity between agents (p ≥ 0.089) suggesting similar efficacy at the HMN. Sex differences remained with atropine and oxybutynin (p < 0.001 to 0.05) but not omadacycline (p = 0.722). Muscarine at the HMN also decreased motor activity (p < 0.001) but this was not sex-specific (p = 0.849). These findings have translational relevance to antimuscarinic agents in OSA pharmacotherapy and understanding potential sex differences in HMN suppression with increased endogenous acetylcholine related to sparing nicotinic excitation.
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Affiliation(s)
- Sepehr Niakani
- Department of Physiology, University of Toronto, Toronto, Canada
| | - Hattie Liu
- Department of Physiology, University of Toronto, Toronto, Canada
| | - Wen-Ying Liu
- Department of Physiology, University of Toronto, Toronto, Canada
| | - Richard L Horner
- Department of Physiology, University of Toronto, Toronto, Canada.
- Department of Medicine, University of Toronto, 3206 Medical Sciences Building, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada.
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20
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Chen K, Dai Y. Chronic exercise increases excitability of lamina X neurons through enhancement of persistent inward currents and dendritic development in mice. J Physiol 2022; 600:3775-3793. [PMID: 35848453 DOI: 10.1113/jp283037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 07/11/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Chronic exercise alters adaptability of spinal motor system in rodents. Multiple mechanisms are responsible for the adaptation, including regulation of neuronal excitability and change in dendritic morphology. Spinal interneurons in lamina X are a cluster of heterogeneous neurons playing multifunctional roles in the spinal cord, especially in regulating locomotor activity. Chronic exercise in juvenile mice increased excitability of these interneurons and facilitated dendritic development. Mechanisms underlying these changes remain unknown. Lamina X neurons expressed persistent inward currents (PICs) composed of calcium (Ca-PIC) and sodium (Na-PIC) components. The exercise-increased excitability of lamina X neurons was mediated by enhancing Ca-PIC and Na-PIC components and facilitating dendritic length. Na-PIC contributed more to lowering of PIC onset and Ca-PIC to increase of PIC amplitude. This study unveiled novel morphological and ionic mechanisms underlying adaptation of lamina X neurons in rodents during chronic exercise. ABSTRACT Chronic exercise has been shown to enhance excitability of spinal interneurons in rodents. However, the mechanisms underlying this enhancement remain unclear. In this study we investigated adaptability of lamina X neurons with three-week treadmill exercise in mice of P21-P24. Whole-cell path-clamp recording was performed on the interneurons from slices of T12-L4. The experimental results included: (1) Treadmill exercise reduced rheobase by 7.4±2.2 pA (control: 11.3±6.1 pA, n = 12; exercise: 3.8±4.6 pA, n = 13; P = 0.002) and hyperpolarized voltage threshold by 7.1±1.5 mV (control: -36.6±4.6 mV, exercise: -43.7±2.7 mV; P = 0.001). (2) Exercise enhanced persistent inward currents (PICs) with increase of amplitude (control: 140.6±56.3 pA, n = 25; exercise: 225.9±62.5 pA, n = 17; P = 0.001) and hyperpolarization of onset (control: -50.3±3.6 mV, exercise: -56.5±5.5 mV; P = 0.001). (3) PICs consisted of dihydropyridine-sensitive calcium (Ca-PIC) and tetrodotoxin-sensitive sodium (Na-PIC) components. Exercise increased amplitude of both components but hyperpolarized onset of Na-PIC only. (4) Exercise reduced derecruitment current of repetitive firing evoked by current bi-ramp and prolonged firing in falling phase of the bi-ramp. The derecruitment reduction was eliminated by bath application of 3 μM riluzole or 25 μM nimodipine, suggesting that both Na-PIC and Ca-PIC contributed to the exercise-prolonged hysteresis of firing. (5) Exercise facilitated dendritic development with significant increase in dendritic length by 285.1±113 μm (control: 457.8±171.8 μm, n = 12; exercise: 742.9±357 μm, n = 14; P = 0.019). We concluded that three-week treadmill exercise increased excitability of lamina X interneurons through enhancement of PICs and increase of dendritic length. This study provided insight into cellular and channel mechanisms underlying adaptation of the spinal motor system in exercise. Abstract figure legend A. B6 mice were randomly divided into control group and exercise group. Control group mice remained sedentary in the cage; exercise group mice completed 60 min treadmill runs each day (6 days/week) for a period of 3 weeks. B. Whole-cell patch clamp recordings were made from lumbar lamina X neurons after three-weeks exercise. C. Exercise facilitated development of dendrites of lamina X neurons. D. Exercise enhanced persistent inward currents. E. Exercise increased excitability of lamina X neurons by hyperpolarizing voltage threshold for action potential generation. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Ke Chen
- Shanghai Key Laboratory of Multidimensional Information Processing, School of Communication and Electronic Engineering, East China Normal University, Shanghai, 200241, China
| | - Yue Dai
- Key Laboratory of Adolescent Health Assessment and Exercise Intervention of Ministry of Education, School of Physical Education and Health Care, East China Normal University, Shanghai, 200241, China.,Shanghai Key Laboratory of Multidimensional Information Processing, School of Communication and Electronic Engineering, East China Normal University, Shanghai, 200241, China
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21
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Events Occurring in the Axotomized Facial Nucleus. Cells 2022; 11:cells11132068. [PMID: 35805151 PMCID: PMC9266054 DOI: 10.3390/cells11132068] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/26/2022] [Accepted: 06/27/2022] [Indexed: 01/27/2023] Open
Abstract
Transection of the rat facial nerve leads to a variety of alterations not only in motoneurons, but also in glial cells and inhibitory neurons in the ipsilateral facial nucleus. In injured motoneurons, the levels of energy metabolism-related molecules are elevated, while those of neurofunction-related molecules are decreased. In tandem with these motoneuron changes, microglia are activated and start to proliferate around injured motoneurons, and astrocytes become activated for a long period without mitosis. Inhibitory GABAergic neurons reduce the levels of neurofunction-related molecules. These facts indicate that injured motoneurons somehow closely interact with glial cells and inhibitory neurons. At the same time, these events allow us to predict the occurrence of tissue remodeling in the axotomized facial nucleus. This review summarizes the events occurring in the axotomized facial nucleus and the cellular and molecular mechanisms associated with each event.
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22
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Khan S. Endoplasmic Reticulum in Metaplasticity: From Information Processing to Synaptic Proteostasis. Mol Neurobiol 2022; 59:5630-5655. [PMID: 35739409 DOI: 10.1007/s12035-022-02916-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 06/05/2022] [Indexed: 11/29/2022]
Abstract
The ER (endoplasmic reticulum) is a Ca2+ reservoir and the unique protein-synthesizing machinery which is distributed throughout the neuron and composed of multiple different structural domains. One such domain is called EMC (endoplasmic reticulum membrane protein complex), pleiotropic nature in cellular functions. The ER/EMC position inside the neurons unmasks its contribution to synaptic plasticity via regulating various cellular processes from protein synthesis to Ca2+ signaling. Since presynaptic Ca2+ channels and postsynaptic ionotropic receptors are organized into the nanodomains, thus ER can be a crucial player in establishing TMNCs (transsynaptic molecular nanocolumns) to shape efficient neural communications. This review hypothesized that ER is not only involved in stress-mediated neurodegeneration but also axon regrowth, remyelination, neurotransmitter switching, information processing, and regulation of pre- and post-synaptic functions. Thus ER might not only be a protein-synthesizing and quality control machinery but also orchestrates plasticity of plasticity (metaplasticity) within the neuron to execute higher-order brain functions and neural repair.
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Affiliation(s)
- Shumsuzzaman Khan
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA.
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Salvany S, Casanovas A, Piedrafita L, Gras S, Calderó J, Esquerda JE. Accumulation of misfolded SOD1 outlines distinct patterns of motor neuron pathology and death during disease progression in a SOD1 G93A mouse model of amyotrophic lateral sclerosis. Brain Pathol 2022; 32:e13078. [PMID: 35584812 PMCID: PMC9616096 DOI: 10.1111/bpa.13078] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 04/11/2022] [Indexed: 12/12/2022] Open
Abstract
Early misfolded superoxide dismutase 1 (mfSOD1) accumulation, motor neuron (MN) degeneration, and microgliosis are hallmark pathological features in SOD1G93A amyotrophic lateral sclerosis (ALS) mice. Because of the different vulnerabilities of distinct MN subtypes, degenerating and surviving MNs coexist in different proportions during disease progression. By examining the expression of misfolded conformers of SOD1 using specific antibodies, we defined distinct MN phenotypes that were evaluated during disease progression and the local neuroinflammatory reaction. The most severe phenotype corresponded to somata of fast‐twitch subtype MNs, which exhibited highly positive mfSOD1 immunostaining and an extreme degree of vacuolar degeneration. Vacuoles, which are of mitochondrial origin, contain mfSOD1 in conjunction with nonmitochondrial proteins, such as chromogranin, CD81, and flotillin. The fusion of ER‐derived vesicles enriched in mfSOD1 with outer mitochondrial membranes is thought to be the primary mechanism for vacuole formation. In addition, the ulterior coalescence of enlarged mitochondria may lead to the formation of giant vacuoles. Vacuolar degeneration is a transient degenerative process occurring early during the presymptomatic stages of the disease in ALS mice. Some vacuolated MNs are also positive for pMLKL, the effector protein of necroptosis. This indicates a newly described mechanism in which extracellular vesicles derived from damaged MNs, via cellular secretion or necroptotic disruption, may be the triggers for initiating neuroinflammation, glial‐mediated neurotoxicity, and disease spreading. Furthermore, as MN degeneration in mutant SOD1 mice is noncell autonomous, the effects of experimentally increasing or decreasing the microglial response on the expression of MN phenotypes were also evaluated, demonstrating bidirectional cross talk signaling between the degree of expression of mfSOD1 and local neuroinflammation. More detailed knowledge regarding these processes occurring long before the end stages of the disease is necessary to identify novel molecular targets for future preclinical testing.
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Affiliation(s)
- Sara Salvany
- Patologia Neuromuscular Experimental, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Anna Casanovas
- Patologia Neuromuscular Experimental, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Lídia Piedrafita
- Patologia Neuromuscular Experimental, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Sílvia Gras
- Patologia Neuromuscular Experimental, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Jordi Calderó
- Patologia Neuromuscular Experimental, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Josep E Esquerda
- Patologia Neuromuscular Experimental, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
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Munoz F, Vicencio-Jimenez S, Jorratt P, Delano PH, Terreros G. Corticofugal and Brainstem Functions Associated With Medial Olivocochlear Cholinergic Transmission. Front Neurosci 2022; 16:866161. [PMID: 35573302 PMCID: PMC9094045 DOI: 10.3389/fnins.2022.866161] [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] [Received: 01/30/2022] [Accepted: 03/24/2022] [Indexed: 11/29/2022] Open
Abstract
Cholinergic transmission is essential for survival and reproduction, as it is involved in several physiological responses. In the auditory system, both ascending and descending auditory pathways are modulated by cholinergic transmission, affecting the perception of sounds. The auditory efferent system is a neuronal network comprised of several feedback loops, including corticofugal and brainstem pathways to the cochlear receptor. The auditory efferent system's -final and mandatory synapses that connect the brain with the cochlear receptor- involve medial olivocochlear neurons and outer hair cells. A unique cholinergic transmission mediates these synapses through α9/α10 nicotinic receptors. To study this receptor, it was generated a strain of mice carrying a null mutation of the Chrna9 gene (α9-KO mice), lacking cholinergic transmission between medial olivocochlear neurons and outer hair cells, providing a unique opportunity to study the role of medial olivocochlear cholinergic transmission in auditory and cognitive functions. In this article, we review behavioral and physiological studies carried out to research auditory efferent function in the context of audition, cognition, and hearing impairments. Auditory studies have shown that hearing thresholds in the α9-KO mice are normal, while more complex auditory functions, such as frequency selectivity and sound localization, are altered. The corticofugal pathways have been studied in α9-KO mice using behavioral tasks, evidencing a reduced capacity to suppress auditory distractors during visual selective attention. Finally, we discuss the evolutionary role of the auditory efferent system detecting vocalizations in noise and its role in auditory disorders, such as the prevention of age-related hearing loss.
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Affiliation(s)
- Felipe Munoz
- Instituto de Ciencias de la Salud, Universidad de O’Higgins, Rancagua, Chile
- Universidad de Valparaíso, Valparaíso, Chile
| | - Sergio Vicencio-Jimenez
- Department of Otolaryngology-Head and Neck Surgery, The Center for Hearing and Balance, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Pascal Jorratt
- National Institute of Mental Health, Klecany, Czechia
- Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Paul H. Delano
- Facultad de Medicina, Neuroscience Department, Universidad de Chile, Santiago, Chile
- Department of Otolaryngology, Hospital Clínico de la Universidad de Chile, Santiago, Chile
- Centro Avanzado de Ingeniería Eléctrica y Electrónica, AC3E, Universidad Técnica Federico Santa María, Valparaíso, Chile
- Facultad de Medicina, Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
| | - Gonzalo Terreros
- Instituto de Ciencias de la Salud, Universidad de O’Higgins, Rancagua, Chile
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25
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Jonaitis J, MacLeod J, Pulver SR. Localization of muscarinic acetylcholine receptor-dependent rhythm-generating modules in the Drosophila larval locomotor network. J Neurophysiol 2022; 127:1098-1116. [PMID: 35294308 PMCID: PMC9018013 DOI: 10.1152/jn.00106.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 03/09/2022] [Accepted: 03/10/2022] [Indexed: 11/22/2022] Open
Abstract
Mechanisms of rhythm generation have been extensively studied in motor systems that control locomotion over terrain in limbed animals; however, much less is known about rhythm generation in soft-bodied terrestrial animals. Here we explored how muscarinic acetylcholine receptor (mAChR)-modulated rhythm-generating networks are distributed in the central nervous system (CNS) of soft-bodied Drosophila larvae. We measured fictive motor patterns in isolated CNS preparations, using a combination of Ca2+ imaging and electrophysiology while manipulating mAChR signaling pharmacologically. Bath application of the mAChR agonist oxotremorine potentiated bilaterally asymmetric activity in anterior thoracic regions and promoted bursting in posterior abdominal regions. Application of the mAChR antagonist scopolamine suppressed rhythm generation in these regions and blocked the effects of oxotremorine. Oxotremorine triggered fictive forward crawling in preparations without brain lobes. Oxotremorine also potentiated rhythmic activity in isolated posterior abdominal CNS segments as well as isolated anterior brain and thoracic regions, but it did not induce rhythmic activity in isolated anterior abdominal segments. Bath application of scopolamine to reduced preparations lowered baseline Ca2+ levels and abolished rhythmic activity. Overall, these results suggest that mAChR signaling plays a role in enabling rhythm generation at multiple sites in the larval CNS. This work furthers our understanding of motor control in soft-bodied locomotion and provides a foundation for study of rhythm-generating networks in an emerging genetically tractable locomotor system.NEW & NOTEWORTHY Using a combination of pharmacology, electrophysiology, and Ca2+ imaging, we find that signaling through mACh receptors plays a critical role in rhythmogenesis in different regions of the Drosophila larval CNS. mAChR-dependent rhythm generators reside in distal regions of the larval CNS and provide functional substrates for central pattern-generating networks (CPGs) underlying headsweep behavior and forward locomotion. This provides new insights into locomotor CPG operation in soft-bodied animals that navigate over terrain.
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Affiliation(s)
- Julius Jonaitis
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, United Kingdom
| | - James MacLeod
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, United Kingdom
| | - Stefan R Pulver
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, United Kingdom
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26
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Recabal-Beyer AJ, Senecal JMM, Senecal JEM, Lynn BD, Nagy JI. On the Organization of Connexin36 Expression in Electrically Coupled Cholinergic V0c Neurons (Partition Cells) in the Spinal Cord and Their C-terminal Innervation of Motoneurons. Neuroscience 2022; 485:91-115. [PMID: 35090881 DOI: 10.1016/j.neuroscience.2022.01.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 01/07/2022] [Accepted: 01/19/2022] [Indexed: 12/13/2022]
Abstract
Large cholinergic neurons (V0c neurons; aka, partition cells) in the spinal cord project profusely to motoneurons on which they form C-terminal contacts distinguished by their specialized postsynaptic subsurface cisterns (SSCs). The V0c neurons are known to be rhythmically active during locomotion and release of acetylcholine (ACh) from their terminals is known to modulate the excitability of motoneurons in what appears to be a task-dependent manner. Here, we present evidence that a subpopulation of V0c neurons express the gap junction forming protein connexin36 (Cx36), indicating that they are coupled by electrical synapses. Based on immunofluorescence imaging and the use of Cx36BAC-enhanced green fluorescent protein (eGFP) mice in which C-terminals immunolabelled for their marker vesicular acetylcholine transporter (vAChT) are also labelled for eGFP, we found a heterogeneous distribution of eGFP+ C-terminals on motoneurons at cervical, thoracic and lumber spinal levels. The density of C-terminals on motoneurons varied as did the proportion of those that were eGFP+ vs. eGFP-. We present evidence that fast vs. slow motoneurons have a greater abundance of these terminals and fast motoneurons also have the highest density that were eGFP+. Thus, our results indicate that a subpopulation of V0c neurons projects preferentially to fast motoneurons, suggesting that the capacity for synchronous activity conferred by electrical synapses among networks of coupled V0c neurons enhances their dynamic capabilities for synchronous regulation of motoneuron excitability during high muscle force generation. The eGFP+ vs. eGFP- V0c neurons were more richly innervated by serotonergic terminals, suggesting their greater propensity for regulation by descending serotonergic systems.
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Affiliation(s)
- A J Recabal-Beyer
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
| | - J M M Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
| | - J E M Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
| | - B D Lynn
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
| | - J I Nagy
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada.
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27
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Cholinergic modulation of persistent inward currents is mediated by activating muscarinic receptors of serotonergic neurons in the brainstem of ePet-EYFP mice. Exp Brain Res 2022; 240:1177-1189. [PMID: 35166863 DOI: 10.1007/s00221-022-06322-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 02/02/2022] [Indexed: 11/04/2022]
Abstract
Persistent inward currents (PICs) play important roles in regulating neural excitability. Results from our previous studies showed that serotonergic (5-HT) neurons of the brainstem expressed PICs. However, little is known about cholinergic (ACh) modulation of PICs in the 5-HT neurons. The whole-cell patch-clamp recordings were performed in the brainstem slices of ePet-EYFP mice to investigate the electrophysiological properties of PICs with cholinergic modulation. PICs in 5-HT neurons were activated at - 51.4 ± 3.7 mV with the amplitude of - 171.6 ± 48.9 pA (n = 71). Bath application of 20-25 μM ACh increased the amplitude by 79.1 ± 42.5 pA (n = 23, p < 0.001) and hyperpolarized the onset voltage by 2.2 ± 2.7 mV (n = 23, p < 0.01) and half-maximal activation by 3.6 ± 2.7 mV (n = 6, p < 0.01). Muscarine mimicked the effects of ACh on PICs, while bath application of nicotine (15-20 μM) did not induce substantial change in the PICs (n = 9). Muscarine enhanced the amplitude of PICs by 100.0 ± 27.4 pA (n = 28, p < 0.001) and lowered the onset voltage by 2.8 ± 1.2 mV (n = 28, p < 0.001) and the half-maximal activation by 2.9 ± 1.4 mV. ACh-induced increase of amplitude and hyperpolarization of onset voltage were blocked by 3-5 μM atropine. Furthermore, the muscarine-induced enhancement of the PICs was antagonized by 5 μM 4-DAMP, the antagonist of M3 receptor, while the antagonists of M1 (Telenzepine, 5 μM) and M5 (VU6008667, 5 μM) receptors did not significantly affect the PIC enhancement. This study suggested that ACh potentiated PICs in 5-HT neurons of the brainstem by activating muscarinic M3 receptor.
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Abstract
The sudden loss of movement after spinal cord injury (SCI) is life-changing and is a major impetus to study spinal cord motor system plasticity and devise novel repair strategies. This review focuses on the motor cortex and the corticospinal tract, which are key to producing voluntary movements. The motor cortex projects directly to the spinal cord, via the corticospinal tract, and indirectly, via relays in the brain stem. With loss of the corticospinal tract after SCI, the indirect paths may bypass the injury and play an important role in voluntary control. In health and after injury, the spinal cord is a key site for activity-dependent neuroplasticity of the corticospinal system. Three kinds of activity-dependent plasticity have been identified: (1) corticospinal tract axon sprouting after electrical stimulation of the motor cortex; (2) synaptic competition between corticospinal tract and proprioceptive afferent fiber terminations; and (3) long-term potentiation (LTP) at the corticospinal tract-spinal interneuron synapse. SCI damages descending motor pathway connections and, in turn, triggers a loss of down-stream activity-dependent processes. This activity loss produces spinal interneuron degeneration and several activity-dependent maladaptive changes that underly hyperreflexia, spasticity, and spasms. Animal studies show that phasic electrical and tonic direct current stimulation can be used to supplement activity after SCI to reduce the activity-dependent degenerative and maladaptive changes. Importantly, when applied chronically neuromodulation recruits spinal neuroplasticity to improve function after SCI by promoting activity-dependent corticospinal axon sprouting and synapse formation. This helps establish new functional connections and strengthens spared connections. Combining neuromodulation to promote repair and motor rehabilitation to train circuits can most effectively promote motor recovery.
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Affiliation(s)
- John H Martin
- Department of Molecular, Cellular, and Biomedical Sciences, Center for Discovery and Innovation, City University of New York School of Medicine, New York, NY, United States; Neuroscience Program, Graduate Center of the City University of New York, New York, NY, United States.
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29
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Electrical Properties of Adult Mammalian Motoneurons. ADVANCES IN NEUROBIOLOGY 2022; 28:191-232. [PMID: 36066827 DOI: 10.1007/978-3-031-07167-6_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Motoneurons are the 'final common path' between the central nervous system (that intends, selects, commands, and organises movement) and muscles (that produce the behaviour). Motoneurons are not passive relays, but rather integrate synaptic activity to appropriately tune output (spike trains) and therefore the production of muscle force. In this chapter, we focus on studies of mammalian motoneurons, describing their heterogeneity whilst providing a brief historical account of motoneuron recording techniques. Next, we describe adult motoneurons in terms of their passive, transition, and active (repetitive firing) properties. We then discuss modulation of these properties by somatic (C-boutons) and dendritic (persistent inward currents) mechanisms. Finally, we briefly describe select studies of human motor unit physiology and relate them to findings from animal preparations discussed earlier in the chapter. This interphyletic approach to the study of motoneuron physiology is crucial to progress understanding of how these diverse neurons translate intention into behaviour.
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Jakovcevski I, Schachner M. Perforin affects regeneration in a mouse spinal cord injury model. Int J Neurosci 2022; 132:1-12. [PMID: 32672480 DOI: 10.1080/00207454.2020.1796662] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/11/2020] [Accepted: 07/01/2020] [Indexed: 02/05/2023]
Abstract
MATERIALS AND METHODS Locomotor outcomes in perforin-deficient (Pfp-/-) mice and wild-type littermate controls were measured after severe compression injury of the lower thoracic spinal cord up to six weeks after injury. RESULTS According to both the Basso mouse scale score and single frame motion analysis, motor recovery of Pfp-/- mice was similar to wild-type controls. Interestingly, immunohistochemical analysis of cell types at six weeks after injury showed enhanced cholinergic reinnervation of spinal motor neurons caudal to the lesion site and neurofilament-positive structures at the injury site in Pfp-/- mice, whereas numbers of microglia/macrophages and astrocytes were decreased compared with controls. CONCLUSIONS We conclude that, although, loss of perforin does not change the locomotor outcome after injury, it beneficially affects diverse cellular features, such as number of axons, cholinergic synapses, astrocytes and microglia/macrophages at or caudal to the lesion site. Perforin's ability to contribute to Rag2's influence on locomotion was observed in mice doubly deficient in perforin and Rag2 which recovered better than Rag2-/- or Pfp-/- mice, suggesting that natural killer cells can cooperate with T- and B-cells in spinal cord injury.
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Affiliation(s)
- Igor Jakovcevski
- Center for Molecular Neurobiology Hamburg, University Hospital Hamburg-Eppendorf, Hamburg, Germany
| | - Melitta Schachner
- Center for Molecular Neurobiology Hamburg, University Hospital Hamburg-Eppendorf, Hamburg, Germany
- Center for Neuroscience, Shantou University Medical College, Shantou, Guangdong, China
- Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA
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Sharples SA, Miles GB. Maturation of persistent and hyperpolarization-activated inward currents shapes the differential activation of motoneuron subtypes during postnatal development. eLife 2021; 10:e71385. [PMID: 34783651 PMCID: PMC8641952 DOI: 10.7554/elife.71385] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 11/15/2021] [Indexed: 12/15/2022] Open
Abstract
The size principle underlies the orderly recruitment of motor units; however, motoneuron size is a poor predictor of recruitment amongst functionally defined motoneuron subtypes. Whilst intrinsic properties are key regulators of motoneuron recruitment, the underlying currents involved are not well defined. Whole-cell patch-clamp electrophysiology was deployed to study intrinsic properties, and the underlying currents, that contribute to the differential activation of delayed and immediate firing motoneuron subtypes. Motoneurons were studied during the first three postnatal weeks in mice to identify key properties that contribute to rheobase and may be important to establish orderly recruitment. We find that delayed and immediate firing motoneurons are functionally homogeneous during the first postnatal week and are activated based on size, irrespective of subtype. The rheobase of motoneuron subtypes becomes staggered during the second postnatal week, which coincides with the differential maturation of passive and active properties, particularly persistent inward currents. Rheobase of delayed firing motoneurons increases further in the third postnatal week due to the development of a prominent resting hyperpolarization-activated inward current. Our results suggest that motoneuron recruitment is multifactorial, with recruitment order established during postnatal development through the differential maturation of passive properties and sequential integration of persistent and hyperpolarization-activated inward currents.
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Affiliation(s)
- Simon A Sharples
- School of Psychology and Neuroscience, University of St AndrewsSt AndrewsUnited Kingdom
| | - Gareth B Miles
- School of Psychology and Neuroscience, University of St AndrewsSt AndrewsUnited Kingdom
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Hongo Y, Matsui T, Nakata T, Furukawa H, Ono T, Kaida K, Suzuki K, Miyahira Y, Kobayashi Y. Morphological characterization of cholinergic partition cells: A transmitter-specific tracing study by Cre/lox-dependent viral gene expression. Ann Anat 2021; 240:151857. [PMID: 34785323 DOI: 10.1016/j.aanat.2021.151857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 11/04/2021] [Accepted: 11/05/2021] [Indexed: 10/19/2022]
Abstract
BACKGROUND Partition cells are cholinergic interneurons located in lamina VII of the spinal cord. Some partition cells are the source of the cholinergic boutons, known as C-terminals or C-boutons, that modulate the activity of spinal motor neurons. Therefore, partition cells might play an important role in motor control. Previous studies categorized partition cells into three groups (medial, intermediate, and lateral partition cells) according to their distance from the central canal. However, the morphological characteristics of the three groups remain obscure. METHODS To analyze the morphology of partition cells, we developed an efficient technique for visualization of specific neurons at single-cell level in particular positions using adenovirus vectors and Cre/lox mediated recombination. Cre/lox conditional vectors were injected into the spinal cord of choline acetyltransferase-Cre transgenic mice, and partition cells labeled by green fluorescent protein were reconstructed from histological serial sections at the single-cell level. RESULTS This technique allowed for the visualization of partition cells at high resolution and revealed that partition cells had various patterns of dendrite orientations and fields. Most of the visualized partition cells had more than 60% of their dendrites located in lamina VII of the spinal cord. Partition cells had dendrites extending into various Rexed's laminae (V, VI, VII, VIII, IX, and X), but none of the cells had dendrites extending dorsal to lamina IV. The dendrites of partition cells terminated both ipsilaterally and bilaterally. We also found that C-terminals on motor neurons may be derived from the middle/outer group of partition cells. CONCLUSIONS Our results indicated that partition cells have various morphological features of the dendritic pattern and may receive differential inputs. Our results suggested that C-terminals originate not only from medial but also from intermediate/lateral cholinergic partition cells. The present study suggests that intermediate/lateral partition cells modulate activities of motor neurons through C-terminal synapses.
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Affiliation(s)
- Yu Hongo
- Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Saitama, Japan; Department of Neurology, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Toshiyasu Matsui
- Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Saitama, Japan; Laboratory of Veterinary Anatomy, Faculty of Veterinary Medicine, Okayama University of Science, Imabari, Ehime, Japan
| | - Takahiro Nakata
- Department of Molecular and Cellular Anatomy, Faculty of Health Promotional Sciences, Tokoha University, Shizuoka, Japan; Department of Health Science, Ishikawa Prefectural Nursing University, Ishikawa, Japan.
| | - Hiroyo Furukawa
- Department of Health Science, Ishikawa Prefectural Nursing University, Ishikawa, Japan; Department of Clinical Nutrition, Ageo Central General Hospital, Saitama, Japan
| | - Takeshi Ono
- Department of Global Infectious Diseases and Tropical Medicine, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Kenichi Kaida
- Department of Neurology, National Defense Medical College, Tokorozawa, Saitama, Japan; Department of Neurology, Saitama Medical Center, Saitama Medical University, Kawagoe, Saitama, Japan
| | - Kazushi Suzuki
- Department of Neurology, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Yasushi Miyahira
- Department of Global Infectious Diseases and Tropical Medicine, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Yasushi Kobayashi
- Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Saitama, Japan.
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Guo W, Fan S, Xiao D, Dong H, Xu G, Wan Z, Ma Y, Wang Z, Xue T, Zhou Y, Li Y, Xiong W. A Brainstem reticulotegmental neural ensemble drives acoustic startle reflexes. Nat Commun 2021; 12:6403. [PMID: 34737329 PMCID: PMC8568936 DOI: 10.1038/s41467-021-26723-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 10/20/2021] [Indexed: 11/21/2022] Open
Abstract
The reticulotegmental nucleus (RtTg) has long been recognized as a crucial component of brainstem reticular formation (RF). However, the function of RtTg and its related circuits remain elusive. Here, we report a role of the RtTg in startle reflex, a highly conserved innate defensive behaviour. Optogenetic activation of RtTg neurons evokes robust startle responses in mice. The glutamatergic neurons in the RtTg are significantly activated during acoustic startle reflexes (ASR). Chemogenetic inhibition of the RtTg glutamatergic neurons decreases the ASR amplitudes. Viral tracing reveals an ASR neural circuit that the cochlear nucleus carrying auditory information sends direct excitatory innervations to the RtTg glutamatergic neurons, which in turn project to spinal motor neurons. Together, our findings describe a functional role of RtTg and its related neural circuit in startle reflexes, and demonstrate how the RF connects auditory system with motor functions.
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Affiliation(s)
- Weiwei Guo
- grid.59053.3a0000000121679639Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China
| | - Sijia Fan
- grid.59053.3a0000000121679639Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China
| | - Dan Xiao
- grid.59053.3a0000000121679639Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China
| | - Hui Dong
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, 100871 China
| | - Guangwei Xu
- grid.59053.3a0000000121679639Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China
| | - Zhikun Wan
- grid.59053.3a0000000121679639Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China
| | - Yuqian Ma
- grid.59053.3a0000000121679639Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China
| | - Zhen Wang
- grid.16821.3c0000 0004 0368 8293Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, P.R. China
| | - Tian Xue
- grid.59053.3a0000000121679639Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China ,grid.9227.e0000000119573309Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031 China
| | - Yifeng Zhou
- grid.59053.3a0000000121679639Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China
| | - Yulong Li
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, 100871 China ,grid.11135.370000 0001 2256 9319PKU-IDG–McGovern Institute for Brain Research, Beijing, 100871 China
| | - Wei Xiong
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026, China. .,Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China.
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Urban LS, Thornton MA, Ingraham Dixie KL, Dale EA, Zhong H, Phelps PE, Burdick JW, Edgerton VR. Formation of a novel supraspinal-spinal connectome that relearns the same motor task after complete paralysis. J Neurophysiol 2021; 126:957-966. [PMID: 34406891 DOI: 10.1152/jn.00422.2020] [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] [Indexed: 11/22/2022] Open
Abstract
Having observed that electrical spinal cord stimulation and training enabled four patients with paraplegia with motor complete paralysis to regain voluntary leg movement, the underlying mechanisms involved in forming the newly established supraspinal-spinal functional connectivity have become of great interest. van den Brand et al. (Science 336: 1182-1185, 2012) subsequently, demonstrated the recovery, in response to spinal electro-neuromodulation and locomotor training, of voluntary stepping of the lower limbs in rats that received a lesion that is assumed to eliminate all long-descending cortical axons that project to lumbosacral segments. Here, we used a similar spinal lesion in rats to eliminate long-descending axons to determine whether a novel, trained motor behavior triggered by a unique auditory cue learned before a spinal lesion, could recover after the lesion. Hindlimb stepping recovered 1 mo after the spinal injury, but only after 2 mo, the novel and unique audio-triggered behavior was recovered, meaning that not only was a novel connectivity formed but also further evidence suggested that this highly unique behavioral response was independent of the recovery of the circuitry that generated stepping. The unique features of the newly formed supraspinal-spinal connections that mediated the recovery of the trained behavior is consistent with a guidance mechanism(s) that are highly use dependent.NEW & NOTEWORTHY Electrical spinal cord stimulation has enabled patients with paraplegia to regain voluntary leg movement, and so the underlying mechanisms involved in this recovery are of great interest. Here, we demonstrate in rodents the recovery of trained motor behavior after a spinal lesion. Rodents were trained to kick their right hindlimb in response to an auditory cue. This behavior recovered 2 mo after the paralyzing spinal cord injury but only with the assistance of electrical spinal cord stimulation.
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Affiliation(s)
- Luke Stuart Urban
- Computation and Neural Systems, California Institute of Technology, Pasadena, California
| | - Michael A Thornton
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California
| | - Katie L Ingraham Dixie
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California
| | - Erica A Dale
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California
| | - Hui Zhong
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California
| | - Patricia E Phelps
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California
| | - Joel W Burdick
- Computation and Neural Systems, California Institute of Technology, Pasadena, California
| | - V Reggie Edgerton
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California.,Department of Neurobiology, University of California, Los Angeles, California.,Department of Neurosurgery, University of California, Los Angeles, California.,Brain Research Institute, University of California, Los Angeles, California.,Institut Guttmann, Hospital de Neurorehabilitació, Institut Universitari adscrit a la Universitat Autònoma de Barcelona, Badalona, Barcelona, Spain
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Locomotion dependent neuron-glia interactions control neurogenesis and regeneration in the adult zebrafish spinal cord. Nat Commun 2021; 12:4857. [PMID: 34381039 PMCID: PMC8357999 DOI: 10.1038/s41467-021-25052-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 07/21/2021] [Indexed: 01/09/2023] Open
Abstract
Physical exercise stimulates adult neurogenesis, yet the underlying mechanisms remain poorly understood. A fundamental component of the innate neuroregenerative capacity of zebrafish is the proliferative and neurogenic ability of the neural stem/progenitor cells. Here, we show that in the intact spinal cord, this plasticity response can be activated by physical exercise by demonstrating that the cholinergic neurotransmission from spinal locomotor neurons activates spinal neural stem/progenitor cells, leading to neurogenesis in the adult zebrafish. We also show that GABA acts in a non-synaptic fashion to maintain neural stem/progenitor cell quiescence in the spinal cord and that training-induced activation of neurogenesis requires a reduction of GABAA receptors. Furthermore, both pharmacological stimulation of cholinergic receptors, as well as interference with GABAergic signaling, promote functional recovery after spinal cord injury. Our findings provide a model for locomotor networks’ activity-dependent neurogenesis during homeostasis and regeneration in the adult zebrafish spinal cord. The mechanisms stimulating adult neurogenesis are unclear. Here, the authors show the contribution of cholinergic and GABAergic signalling within the locomotor network to spinal cord neurogenesis during homeostasis and regeneration, showing neurogenesis depends on circuit activity in the adult zebrafish.
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36
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Kissane RWP, Ghaffari-Rafi A, Tickle PG, Chakrabarty S, Egginton S, Brownstone RM, Smith CC. C-bouton components on rat extensor digitorum longus motoneurons are resistant to chronic functional overload. J Anat 2021; 241:1157-1168. [PMID: 33939175 PMCID: PMC9558151 DOI: 10.1111/joa.13439] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 02/06/2023] Open
Abstract
Mammalian motor systems adapt to the demands of their environment. For example, muscle fibre types change in response to increased load or endurance demands. However, for adaptations to be effective, motoneurons must adapt such that their properties match those of the innervated muscle fibres. We used a rat model of chronic functional overload to assess adaptations to both motoneuron size and a key modulatory synapse responsible for amplification of motor output, C‐boutons. Overload of extensor digitorum longus (EDL) muscles was induced by removal of their synergists, tibialis anterior muscles. Following 21 days survival, EDL muscles showed an increase in fatigue resistance and a decrease in force output, indicating a shift to a slower phenotype. These changes were reflected by a decrease in motoneuron size. However, C‐bouton complexes remained largely unaffected by overload. The C‐boutons themselves, quantified by expression of vesicular acetylcholine transporter, were similar in size and density in the control and overload conditions. Expression of the post‐synaptic voltage‐gated potassium channel (KV2.1) was also unchanged. Small conductance calcium‐activated potassium channels (SK3) were expressed in most EDL motoneurons, despite this being an almost exclusively fast motor pool. Overload induced a decrease in the proportion of SK3+ cells, however, there was no change in density or size of clusters. We propose that reductions in motoneuron size may promote early recruitment of EDL motoneurons, but that C‐bouton plasticity is not necessary to increase the force output required in response to muscle overload.
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Affiliation(s)
- Roger W P Kissane
- Institute of Ageing & Chronic Disease, University of Liverpool, Liverpool, UK.,School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Arash Ghaffari-Rafi
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Peter G Tickle
- School of Biomedical Sciences, University of Leeds, Leeds, UK
| | | | - Stuart Egginton
- School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Robert M Brownstone
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Calvin C Smith
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
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37
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Alkaslasi MR, Piccus ZE, Hareendran S, Silberberg H, Chen L, Zhang Y, Petros TJ, Le Pichon CE. Single nucleus RNA-sequencing defines unexpected diversity of cholinergic neuron types in the adult mouse spinal cord. Nat Commun 2021; 12:2471. [PMID: 33931636 PMCID: PMC8087807 DOI: 10.1038/s41467-021-22691-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 03/25/2021] [Indexed: 02/05/2023] Open
Abstract
In vertebrates, motor control relies on cholinergic neurons in the spinal cord that have been extensively studied over the past hundred years, yet the full heterogeneity of these neurons and their different functional roles in the adult remain to be defined. Here, we develop a targeted single nuclear RNA sequencing approach and use it to identify an array of cholinergic interneurons, visceral and skeletal motor neurons. Our data expose markers for distinguishing these classes of cholinergic neurons and their rich diversity. Specifically, visceral motor neurons, which provide autonomic control, can be divided into more than a dozen transcriptomic classes with anatomically restricted localization along the spinal cord. The complexity of the skeletal motor neurons is also reflected in our analysis with alpha, gamma, and a third subtype, possibly corresponding to the elusive beta motor neurons, clearly distinguished. In combination, our data provide a comprehensive transcriptomic description of this important population of neurons that control many aspects of physiology and movement and encompass the cellular substrates for debilitating degenerative disorders.
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Affiliation(s)
- Mor R Alkaslasi
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
- Department of Neuroscience, Brown University, Providence, RI, USA
| | - Zoe E Piccus
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
- Department of Neuroscience, Brown University, Providence, RI, USA
| | - Sangeetha Hareendran
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Hanna Silberberg
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Li Chen
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Yajun Zhang
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Timothy J Petros
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Claire E Le Pichon
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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38
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Dhanasobhon D, Medrano MC, Becker LJ, Moreno-Lopez Y, Kavraal S, Bichara C, Schlichter R, Inquimbert P, Yalcin I, Cordero-Erausquin M. Enhanced analgesic cholinergic tone in the spinal cord in a mouse model of neuropathic pain. Neurobiol Dis 2021; 155:105363. [PMID: 33845128 DOI: 10.1016/j.nbd.2021.105363] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 03/12/2021] [Accepted: 03/31/2021] [Indexed: 11/30/2022] Open
Abstract
Endogenous acetylcholine (ACh) is an important modulator of nociceptive sensory processing in the spinal cord. An increased level of spinal ACh induces analgesia both in humans and rodents while interfering with cholinergic signaling is allodynic, demonstrating that a basal tone of spinal ACh modulates nociceptive responses in naïve animals. The plasticity undergone by this cholinergic system in chronic pain situation is unknown, and the mere presence of this tone in neuropathic animals is controversial. We have addressed these issues in mice through behavioral experiments, histology, electrophysiology and molecular biology, in the cuff model of peripheral neuropathy. Our behavior experiments demonstrate the persistence, and even increased impact of the analgesic cholinergic tone acting through nicotinic receptors in cuff animals. The neuropathy does not affect the number or membrane properties of dorsal horn cholinergic neurons, nor specifically the frequency of their synaptic inputs. The alterations thus appear to be in the neurons receiving the cholinergic signaling, which is confirmed by the fact that subthreshold doses of acetylcholinesterase (AChE) inhibitors in sham animals become anti-allodynic in cuff mice and by the altered expression of the β2 nicotinic receptor subunit. Our results demonstrate that endogenous cholinergic signaling can be manipulated to relieve mechanical allodynia in animal models of peripheral neuropathy. Until now, AChE inhibitors have mainly been used in the clinics in situations of acute pain (parturition, post-operative). The fact that lower doses (thus with fewer side effects) could be efficient in chronic pain conditions opens new avenues for the treatment of neuropathic pain. SIGNIFICANCE STATEMENT: Chronic pain continues to be the most common cause of disability that impairs the quality of life, accruing enormous and escalating socio-economic costs. A better understanding of the plasticity of spinal neuronal networks, crucially involved in nociceptive processing, could help designing new therapeutic avenues. We here demonstrate that chronic pain modifies the spinal nociceptive network in such a way that it becomes more sensitive to cholinergic modulations. The spinal cholinergic system is responsible for an analgesic tone that can be exacerbated by acetylcholinesterase inhibitors, a property used in the clinic to relief acute pain (child birth, post-op). Our results suggest that lower doses of acetylcholinesterases, with even fewer side effects, could be efficient to relieve chronic pain.
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Affiliation(s)
- Dhanasak Dhanasobhon
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Maria-Carmen Medrano
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Léa J Becker
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Yunuen Moreno-Lopez
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Sehrazat Kavraal
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Charlotte Bichara
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Rémy Schlichter
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Perrine Inquimbert
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Ipek Yalcin
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France
| | - Matilde Cordero-Erausquin
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 67000 Strasbourg, France; University of Strasbourg Institute for Advanced Study (USIAS), 67000 Strasbourg, France.
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39
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Sharif H, Alexander H, Azam A, Martin JH. Dual motor cortex and spinal cord neuromodulation improves rehabilitation efficacy and restores skilled locomotor function in a rat cervical contusion injury model. Exp Neurol 2021; 341:113715. [PMID: 33819448 PMCID: PMC10150584 DOI: 10.1016/j.expneurol.2021.113715] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/14/2021] [Accepted: 03/31/2021] [Indexed: 01/11/2023]
Abstract
Motor recovery after spinal cord injury is limited due to sparse descending pathway axons caudal to the injury. Rehabilitation is the primary treatment for paralysis in humans with SCI, but only produces modest functional recovery. Here, we determined if dual epidural motor cortex (M1) intermittent theta burst stimulation (iTBS) and cathodal transcutaneous spinal direct stimulation (tsDCS) enhances the efficacy of rehabilitation in improving motor function after cervical SCI. iTBS produces CST axon sprouting and tsDCS enhances M1-evoked spinal activity and muscle contractions after SCI. Rats were trained to perform the horizontal ladder task. Animals received a moderate midline C4 contusion, producing bilateral forelimb impairments. After 2 weeks, animals either received 10 days of iTBS+tsDCS or no stimulation; subsequently, all animals received 6 weeks of daily rehabilitation on the horizontal ladder task. Lesion size was not different in the two animal groups. Rehabilitation alone improved performance by a 22% reduction in skilled locomotion error rate, whereas stimulation+rehabilitation was markedly more effective (52%), and restored error rate to pre-injury levels. Stimulation+rehabilitation significantly increased CST axon length caudal to the injury and the amount of ventral horn label was positively correlated with functional improvement. The stimulation+rehabilitation group had significantly less proprioceptive afferent terminal labelling in the intermediate zone and fewer synapses on motoneurons . Afferent fiber terminal labeling was negatively correlated with motor recovery. Thus, the dual neuromodulation protocol promotes adaptive plasticity in corticospinal and proprioceptive afferents networks after contusion SCI, leading to enhanced rehabilitation efficacy and recovery of skilled locomotion.
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Affiliation(s)
- Hisham Sharif
- Department of Molecular, Cellular, and Biomedical Sciences, Center for Discovery and Innovation, City University of New York School of Medicine, New York, NY, USA
| | - Heather Alexander
- Department of Molecular, Cellular, and Biomedical Sciences, Center for Discovery and Innovation, City University of New York School of Medicine, New York, NY, USA
| | - Anika Azam
- Department of Molecular, Cellular, and Biomedical Sciences, Center for Discovery and Innovation, City University of New York School of Medicine, New York, NY, USA
| | - John H Martin
- Department of Molecular, Cellular, and Biomedical Sciences, Center for Discovery and Innovation, City University of New York School of Medicine, New York, NY, USA; Neuroscience Program, Graduate Center of the City University of New York, New York, NY, USA.
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40
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Blum JA, Klemm S, Shadrach JL, Guttenplan KA, Nakayama L, Kathiria A, Hoang PT, Gautier O, Kaltschmidt JA, Greenleaf WJ, Gitler AD. Single-cell transcriptomic analysis of the adult mouse spinal cord reveals molecular diversity of autonomic and skeletal motor neurons. Nat Neurosci 2021; 24:572-583. [PMID: 33589834 PMCID: PMC8016743 DOI: 10.1038/s41593-020-00795-0] [Citation(s) in RCA: 91] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Accepted: 12/23/2020] [Indexed: 01/30/2023]
Abstract
The spinal cord is a fascinating structure that is responsible for coordinating movement in vertebrates. Spinal motor neurons control muscle activity by transmitting signals from the spinal cord to diverse peripheral targets. In this study, we profiled 43,890 single-nucleus transcriptomes from the adult mouse spinal cord using fluorescence-activated nuclei sorting to enrich for motor neuron nuclei. We identified 16 sympathetic motor neuron clusters, which are distinguishable by spatial localization and expression of neuromodulatory signaling genes. We found surprising skeletal motor neuron heterogeneity in the adult spinal cord, including transcriptional differences that correlate with electrophysiologically and spatially distinct motor pools. We also provide evidence for a novel transcriptional subpopulation of skeletal motor neuron (γ*). Collectively, these data provide a single-cell transcriptional atlas ( http://spinalcordatlas.org ) for investigating the organizing molecular logic of adult motor neuron diversity, as well as the cellular and molecular basis of motor neuron function in health and disease.
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Affiliation(s)
- Jacob A Blum
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
- Stanford Neurosciences Graduate Program, Stanford University School of Medicine, Stanford, CA, USA
| | - Sandy Klemm
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Jennifer L Shadrach
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Kevin A Guttenplan
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
- Stanford Neurosciences Graduate Program, Stanford University School of Medicine, Stanford, CA, USA
| | - Lisa Nakayama
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Arwa Kathiria
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Phuong T Hoang
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
- Department of Neurology and Neurological Science, Stanford University School of Medicine, Stanford, CA, USA
| | - Olivia Gautier
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
- Stanford Neurosciences Graduate Program, Stanford University School of Medicine, Stanford, CA, USA
| | - Julia A Kaltschmidt
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - William J Greenleaf
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
- Department of Applied Physics, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.
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41
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Matzner H, Zelinger M, Cherniak M, Anglister L, Lev-Tov A. Rhythmogenic networks are potently modulated by activation of muscarinic acetylcholine receptors in the rodent spinal cord. J Neurochem 2021; 158:1263-1273. [PMID: 33735482 DOI: 10.1111/jnc.15354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 03/10/2021] [Accepted: 03/11/2021] [Indexed: 02/02/2023]
Abstract
Electrical stimulation of the spinal cord is a potent means for activating mammalian stepping in the absence of the descending control from the brain. Previously, we have shown that stimulation of pain delivering (Aδ) sacrocaudal afferents (SCA) has a powerful capacity to activate the sacral and lumbar rhythmogenic networks in the neonatal rodent spinal cord. Relatively little is known about the neural pathways involved in activation of the locomotor networks by Aδ afferents, on their mechanism of action and on the possibility to modulate their activity. We have shown that elevation of the endogenous level of acetylcholine at the sacral cord by blocking cholinesterase could modulate the SCA-induced locomotor rhythm in a muscarinic receptor-dependent mechanism. Here, we review these and more recent findings and report that controlled stimulation of SCA in the presence of muscarine is a potent activator of the locomotor network. The possible mechanisms involved in the muscarinic modulation of the locomotor rhythm are discussed in terms of the differential projections of sacral relay neurons, activated by SCA stimulation, to the lumbar locomotor rhythm generators, and to their target motoneurons. Altogether, our studies show that manipulations of cholinergic networks offer a simple and powerful means to control the activity of locomotor networks in the absence of supraspinal control.
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Affiliation(s)
- Henry Matzner
- Department of Medical Neurobiology, Institute for Medical Research - Israel-Canada, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Moshe Zelinger
- Department of Medical Neurobiology, Institute for Medical Research - Israel-Canada, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Meir Cherniak
- Department of Medical Neurobiology, Institute for Medical Research - Israel-Canada, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Lili Anglister
- Department of Medical Neurobiology, Institute for Medical Research - Israel-Canada, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Aharon Lev-Tov
- Department of Medical Neurobiology, Institute for Medical Research - Israel-Canada, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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Dempsey LM, Kavanagh JJ. Muscarinic receptor blockade causes postcontraction enhancement in corticospinal excitability following maximal contractions. J Neurophysiol 2021; 125:1269-1278. [PMID: 33625939 DOI: 10.1152/jn.00673.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although synaptic transmission in motor pathways can be regulated by neuromodulators, such as acetylcholine, few studies have examined how cholinergic activity affects cortical and spinal motor circuits following muscle contractions of varying intensities. This was a human, double-blinded, placebo-controlled, crossover study. Participants attended two sessions where they were administered either a placebo or 25 mg of promethazine. Electromyography of the abductor digiti minimi (ADM) was measured for all conditions. Motor evoked potentials (MEPs) were obtained via motor cortical transcranial magnetic stimulation (TMS), and F waves were obtained via ulnar nerve electrical stimulation. MEPs and F waves were examined: 1) when the muscle was at rest; 2) after the muscle had been active; and 3) after the muscle had been fatigued. MEPs were unaffected by muscarinic receptor blockade when measurements were recorded from resting muscle or following a 50% isometric maximal voluntary contraction (MVC). However, muscarinic receptor blockade increased MEP area following a 10-s MVC (P = 0.019) and following a fatiguing 60-s MVC (P = 0.040). F wave area and persistence were not affected by promethazine for any muscle contraction condition. Corticospinal excitability was influenced by cholinergic effects when voluntary drive to the muscle was high. Given that spinal motoneurone excitability remained unaffected, it is likely that cholinergic effects are influential within the motor cortex during strong muscle contractions. Future research should evaluate how cholinergic effects alter the relationship between subcortical structures and the motor cortex, as well as brainstem neuromodulatory pathways and spinal motoneurons.NEW & NOTEWORTHY The relationship between motor function and cholinergic circuitry in the central nervous system is complex. Although many studies have approached this issue at the cellular level, few studies have examined cholinergic mechanisms in humans performing muscle contractions. This study demonstrates that blockade of muscarinic acetylcholine receptors enhances motor evoked potentials (elicited with transcranial magnetic stimulation) following strong muscle contractions, but not weak muscle contractions.
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Affiliation(s)
- Lisa M Dempsey
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
| | - Justin J Kavanagh
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
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Mille T, Quilgars C, Cazalets J, Bertrand SS. Acetylcholine and spinal locomotor networks: The insider. Physiol Rep 2021; 9:e14736. [PMID: 33527727 PMCID: PMC7851432 DOI: 10.14814/phy2.14736] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Revised: 01/05/2021] [Accepted: 01/07/2021] [Indexed: 01/07/2023] Open
Abstract
This article aims to review studies that have investigated the role of neurons that use the transmitter acetylcholine (ACh) in controlling the operation of locomotor neural networks within the spinal cord. This cholinergic system has the particularity of being completely intraspinal. We describe the different effects exerted by spinal cholinergic neurons on locomotor circuitry by the pharmacological activation or blockade of this propriospinal system, as well as describing its different cellular and subcellular targets. Through the activation of one ionotropic receptor, the nicotinic receptor, and five metabotropic receptors, the M1 to M5 muscarinic receptors, the cholinergic system exerts a powerful control both on synaptic transmission and locomotor network neuron excitability. Although tremendous advances have been made in our understanding of the spinal cholinergic system's involvement in the physiology and pathophysiology of locomotor networks, gaps still remain, including the precise role of the different subtypes of cholinergic neurons as well as their pre- and postsynaptic partners. Improving our knowledge of the propriospinal cholinergic system is of major relevance to finding new cellular targets and therapeutics in countering the debilitating effects of neurodegenerative diseases and restoring motor functions after spinal cord injury.
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Affiliation(s)
- Théo Mille
- Université de BordeauxCNRS UMR 5287INCIABordeauxFrance
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Deardorff AS, Romer SH, Fyffe RE. Location, location, location: the organization and roles of potassium channels in mammalian motoneurons. J Physiol 2021; 599:1391-1420. [DOI: 10.1113/jp278675] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 01/08/2021] [Indexed: 11/08/2022] Open
Affiliation(s)
- Adam S. Deardorff
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine Dayton OH 45435 USA
- Department of Neurology and Internal Medicine, Wright State University Boonshoft School of Medicine Dayton OH 45435 USA
| | - Shannon H. Romer
- Odyssey Systems Environmental Health Effects Laboratory, Navy Medical Research Unit‐Dayton Wright‐Patterson Air Force Base OH 45433 USA
| | - Robert E.W. Fyffe
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine Dayton OH 45435 USA
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Ronzano R, Lancelin C, Bhumbra GS, Brownstone RM, Beato M. Proximal and distal spinal neurons innervating multiple synergist and antagonist motor pools. eLife 2021; 10:70858. [PMID: 34727018 PMCID: PMC8631798 DOI: 10.7554/elife.70858] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 11/01/2021] [Indexed: 11/13/2022] Open
Abstract
Motoneurons (MNs) control muscle contractions, and their recruitment by premotor circuits is tuned to produce accurate motor behaviours. To understand how these circuits coordinate movement across and between joints, it is necessary to understand whether spinal neurons pre-synaptic to motor pools have divergent projections to more than one MN population. Here, we used modified rabies virus tracing in mice to investigate premotor interneurons projecting to synergist flexor or extensor MNs, as well as those projecting to antagonist pairs of muscles controlling the ankle joint. We show that similar proportions of premotor neurons diverge to synergist and antagonist motor pools. Divergent premotor neurons were seen throughout the spinal cord, with decreasing numbers but increasing proportion with distance from the hindlimb enlargement. In the cervical cord, divergent long descending propriospinal neurons were found in contralateral lamina VIII, had large somata, were neither glycinergic, nor cholinergic, and projected to both lumbar and cervical MNs. We conclude that distributed spinal premotor neurons coordinate activity across multiple motor pools and that there are spinal neurons mediating co-contraction of antagonist muscles.
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Affiliation(s)
- Remi Ronzano
- Department of Neuromuscular Diseases, University College LondonLondonUnited Kingdom
| | - Camille Lancelin
- Department of Neuromuscular Diseases, University College LondonLondonUnited Kingdom
| | - Gardave Singh Bhumbra
- Department of Neuroscience Physiology and Pharmacology, University College LondonLondonUnited Kingdom
| | - Robert M Brownstone
- Department of Neuromuscular Diseases, University College LondonLondonUnited Kingdom
| | - Marco Beato
- Neuroscience, Physiology and Pharmacology, University College LondonLondonUnited Kingdom
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Fouad K, Popovich PG, Kopp MA, Schwab JM. The neuroanatomical-functional paradox in spinal cord injury. Nat Rev Neurol 2021; 17:53-62. [PMID: 33311711 PMCID: PMC9012488 DOI: 10.1038/s41582-020-00436-x] [Citation(s) in RCA: 73] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/11/2020] [Indexed: 12/13/2022]
Abstract
Although lesion size is widely considered to be the most reliable predictor of outcome after CNS injury, lesions of comparable size can produce vastly different magnitudes of functional impairment and subsequent recovery. This neuroanatomical-functional paradox is likely to contribute to the many failed attempts to independently replicate findings from animal models of neurotrauma. In humans, the analogous clinical-radiological paradox could explain why individuals with similar injuries can respond differently to rehabilitation. We describe the neuroanatomical-functional paradox in the context of traumatic spinal cord injury (SCI) and discuss the underlying mechanisms of the paradox, including the concepts of lesion-affected and recovery-related networks. We also consider the various secondary complications that further limit the accuracy of outcome prediction in SCI and provide suggestions for how to increase the predictive, translational value of preclinical SCI models.
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Affiliation(s)
- Karim Fouad
- Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada
- Institute for Neuroscience and Mental Health, University of Alberta, Edmonton, AB, Canada
| | - Phillip G Popovich
- Belford Center for Spinal Cord Injury, The Ohio State University, Wexner Medical Center, Columbus, OH, USA
- Center for Brain and Spinal Cord Repair, The Ohio State University, Wexner Medical Center, Columbus, OH, USA
- Department of Neuroscience, The Ohio State University, Wexner Medical Center, Columbus, OH, USA
- The Neurological Institute, The Ohio State University, Wexner Medical Center, Columbus, OH, USA
| | - Marcel A Kopp
- Clinical & Experimental Spinal Cord Injury Research, Department of Neurology with Experimental Neurology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany
- Berlin Institute of Health (QUEST-Center for Transforming Biomedical Research), Berlin, Germany
| | - Jan M Schwab
- Belford Center for Spinal Cord Injury, The Ohio State University, Wexner Medical Center, Columbus, OH, USA.
- Center for Brain and Spinal Cord Repair, The Ohio State University, Wexner Medical Center, Columbus, OH, USA.
- Department of Neuroscience, The Ohio State University, Wexner Medical Center, Columbus, OH, USA.
- The Neurological Institute, The Ohio State University, Wexner Medical Center, Columbus, OH, USA.
- Clinical & Experimental Spinal Cord Injury Research, Department of Neurology with Experimental Neurology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany.
- Spinal Cord Injury Medicine (Neuroplegiology), Department of Neurology, The Ohio State University, Wexner Medical Center, Columbus, OH, USA.
- Department of Physical Medicine and Rehabilitation, The Ohio State University, Wexner Medical Center, Columbus, OH, USA.
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Konsolaki E, Koropouli E, Tsape E, Pothakos K, Zagoraiou L. Genetic Inactivation of Cholinergic C Bouton Output Improves Motor Performance but not Survival in a Mouse Model of Amyotrophic Lateral Sclerosis. Neuroscience 2020; 450:71-80. [DOI: 10.1016/j.neuroscience.2020.07.047] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 07/06/2020] [Accepted: 07/26/2020] [Indexed: 12/17/2022]
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48
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The M-current works in tandem with the persistent sodium current to set the speed of locomotion. PLoS Biol 2020; 18:e3000738. [PMID: 33186352 PMCID: PMC7688130 DOI: 10.1371/journal.pbio.3000738] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 11/25/2020] [Accepted: 10/13/2020] [Indexed: 01/20/2023] Open
Abstract
The central pattern generator (CPG) for locomotion is a set of pacemaker neurons endowed with inherent bursting driven by the persistent sodium current (INaP). How they proceed to regulate the locomotor rhythm remained unknown. Here, in neonatal rodents, we identified a persistent potassium current critical in regulating pacemakers and locomotion speed. This current recapitulates features of the M-current (IM): a subthreshold noninactivating outward current blocked by 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride (XE991) and enhanced by N-(2-chloro-5-pyrimidinyl)-3,4-difluorobenzamide (ICA73). Immunostaining and mutant mice highlight an important role of Kv7.2-containing channels in mediating IM. Pharmacological modulation of IM regulates the emergence and the frequency regime of both pacemaker and CPG activities and controls the speed of locomotion. Computational models captured these results and showed how an interplay between IM and INaP endows the locomotor CPG with rhythmogenic properties. Overall, this study provides fundamental insights into how IM and INaP work in tandem to set the speed of locomotion.
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49
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Sinha N, Heckman CJ, Yang Y. Slowly activating outward membrane currents generate input-output sub-harmonic cross frequency coupling in neurons. J Theor Biol 2020; 509:110509. [PMID: 33022285 DOI: 10.1016/j.jtbi.2020.110509] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 08/16/2020] [Accepted: 09/27/2020] [Indexed: 02/01/2023]
Abstract
A major challenge in understanding spike-time dependent information encoding in the neural system is the non-linear firing response to inputs of the individual neurons. Hence, quantitative exploration of the putative mechanisms of this non-linear behavior is fundamental to formulating the theory of information transfer in the neural system. The objective of this simulation study was to evaluate and quantify the effect of slowly activating outward membrane current, on the non-linearity in the output of a one-compartment Hodgkin-Huxley styled neuron. To evaluate this effect, the peak conductance of the slow potassium channel (gK-slow) was varied from 0% to 200% of its normal value in steps of 33%. Both cross- and iso-frequency coupling between the input and the output of the simulated neuron was computed using a generalized coherence measure, i.e., n:m coherence. With increasing gK-slow, the amount of sub-harmonic cross-frequency coupling, where the output frequencies (1-8 Hz) are lower than the input frequencies (15-35 Hz), increased progressively whereas no change in iso-frequency coupling was observed. Power spectral and phase-space analysis of the neuronal membrane voltage vs. slow potassium channel activation variable showed that the interaction of the slow channel dynamics with the fast membrane voltage dynamics generates the observed sub-harmonic coupling. This study provides quantitative insights into the role of an important membrane mechanism i.e. the slowly activating outward current in generating non-linearities in the output of a neuron.
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Affiliation(s)
- Nirvik Sinha
- Northwestern Interdepartmental Neuroscience Program, Feinberg School of Medicine, Northwestern University, 320 E Superior Street, Morton 1-645, Chicago, IL 60611-3010, USA; Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, 645 N. Michigan Ave., Suite 1100, Chicago, IL 60611, USA
| | - C J Heckman
- Northwestern Interdepartmental Neuroscience Program, Feinberg School of Medicine, Northwestern University, 320 E Superior Street, Morton 1-645, Chicago, IL 60611-3010, USA; Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, 645 N. Michigan Ave., Suite 1100, Chicago, IL 60611, USA; Department of Physiology, Feinberg School of Medicine, Northwestern University, 310 E. Superior Street Morton 5-660, Chicago, IL 60611, USA
| | - Yuan Yang
- Northwestern Interdepartmental Neuroscience Program, Feinberg School of Medicine, Northwestern University, 320 E Superior Street, Morton 1-645, Chicago, IL 60611-3010, USA; Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, 645 N. Michigan Ave., Suite 1100, Chicago, IL 60611, USA; Stephenson School of Biomedical Engineering, University of Oklahoma, 4502 E. 41st St, Tulsa, OK 74135, USA; Laureate Institute for Brain Research, 6655 S Yale Ave, Tulsa, OK 74136, USA.
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50
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Herrando-Grabulosa M, Gaja-Capdevila N, Vela JM, Navarro X. Sigma 1 receptor as a therapeutic target for amyotrophic lateral sclerosis. Br J Pharmacol 2020; 178:1336-1352. [PMID: 32761823 DOI: 10.1111/bph.15224] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 07/13/2020] [Accepted: 07/25/2020] [Indexed: 12/13/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is an adult disease causing a progressive loss of upper and lower motoneurons, muscle paralysis and early death. ALS has a poor prognosis of 3-5 years after diagnosis with no effective cure. The aetiopathogenic mechanisms involved include glutamate excitotoxicity, oxidative stress, protein misfolding, mitochondrial alterations, disrupted axonal transport and inflammation. Sigma non-opioid intracellular receptor 1 (sigma 1 receptor) is a protein expressed in motoneurons, mainly found in the endoplasmic reticulum (ER) on the mitochondria-associated ER membrane (MAM) or in close contact with cholinergic postsynaptic sites. MAMs are sites that allow the assembly of several complexes implicated in essential survival cell functions. The sigma 1 receptor modulates essential mechanisms for motoneuron survival including excitotoxicity, calcium homeostasis, ER stress and mitochondrial dysfunction. This review updates sigma 1 receptor mechanisms and its alterations in ALS, focusing on MAM modulation, which may constitute a novel target for therapeutic strategies. LINKED ARTICLES: This article is part of a themed issue on Neurochemistry in Japan. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.6/issuetoc.
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Affiliation(s)
- Mireia Herrando-Grabulosa
- Institute of Neurosciences, Department Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Bellaterra, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Núria Gaja-Capdevila
- Institute of Neurosciences, Department Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Bellaterra, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - José M Vela
- Esteve Pharmaceuticals S.A., Drug Discovery and Preclinical Development, Barcelona, Spain
| | - Xavier Navarro
- Institute of Neurosciences, Department Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Bellaterra, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Institut Guttmann de Neurorehabilitació, Badalona, Spain
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