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Garcia-Ramirez DL, McGrath JR, Ha NT, Wheel JH, Atoche SJ, Yao L, Stachowski NJ, Giszter SF, Dougherty KJ. Covert actions of epidural stimulation on spinal locomotor circuits. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.18.599598. [PMID: 38948733 PMCID: PMC11213016 DOI: 10.1101/2024.06.18.599598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Spinal circuitry produces the rhythm and patterning of locomotion. However, both descending and sensory inputs are required to initiate and adapt locomotion to the environment. Spinal cord injury (SCI) disrupts descending controls of the spinal cord, producing paralysis. Epidural stimulation (ES) is a promising clinical therapy for motor control recovery and is capable of reactivating the lumbar spinal locomotor networks, yet little is known about the effects of ES on locomotor neurons. Previously, we found that both sensory afferent pathways and serotonin exert mixed excitatory and inhibitory actions on lumbar interneurons involved in the generation of the locomotor rhythm, identified by the transcription factor Shox2. However, after chronic complete SCI, sensory afferent inputs to Shox2 interneurons become almost exclusively excitatory and Shox2 interneurons are supersensitive to serotonin. Here, we investigated the effects of ES on these SCI-induced changes. Inhibitory input from sensory pathways to Shox2 interneurons was maintained and serotonin supersensitivity was not observed in SCI mice that received daily sub-motor threshold ES. Interestingly, the effects of ES were maintained for at least three weeks after the ES was discontinued. In contrast, the effects of ES were not observed in Shox2 interneurons from mice that received ES after the establishment of the SCI-induced changes. Our results demonstrate mechanistic actions of ES at the level of identified spinal locomotor circuit neurons and the effectiveness of early treatment with ES on preservation of spinal locomotor circuitry after SCI, suggesting possible therapeutic benefits prior to the onset of motor rehabilitation.
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Zhou K, Wei W, Yang D, Zhang H, Yang W, Zhang Y, Nie Y, Hao M, Wang P, Ruan H, Zhang T, Wang S, Liu Y. Dual electrical stimulation at spinal-muscular interface reconstructs spinal sensorimotor circuits after spinal cord injury. Nat Commun 2024; 15:619. [PMID: 38242904 PMCID: PMC10799086 DOI: 10.1038/s41467-024-44898-9] [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: 01/12/2023] [Accepted: 01/09/2024] [Indexed: 01/21/2024] Open
Abstract
The neural signals produced by varying electrical stimulation parameters lead to characteristic neural circuit responses. However, the characteristics of neural circuits reconstructed by electrical signals remain poorly understood, which greatly limits the application of such electrical neuromodulation techniques for the treatment of spinal cord injury. Here, we develop a dual electrical stimulation system that combines epidural electrical and muscle stimulation to mimic feedforward and feedback electrical signals in spinal sensorimotor circuits. We demonstrate that a stimulus frequency of 10-20 Hz under dual stimulation conditions is required for structural and functional reconstruction of spinal sensorimotor circuits, which not only activates genes associated with axonal regeneration of motoneurons, but also improves the excitability of spinal neurons. Overall, the results provide insights into neural signal decoding during spinal sensorimotor circuit reconstruction, suggesting that the combination of epidural electrical and muscle stimulation is a promising method for the treatment of spinal cord injury.
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Affiliation(s)
- Kai Zhou
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University; Clinical Research Center of Neurological Disease, The Second Affiliated Hospital of Soochow University, Suzhou, 215123, China
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong, 226001, China
| | - Wei Wei
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University; Clinical Research Center of Neurological Disease, The Second Affiliated Hospital of Soochow University, Suzhou, 215123, China
| | - Dan Yang
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University; Clinical Research Center of Neurological Disease, The Second Affiliated Hospital of Soochow University, Suzhou, 215123, China
- Department of Anatomy, School of Basic Medical Science, Guizhou Medical University, Guiyang, 550025, China
| | - Hui Zhang
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University; Clinical Research Center of Neurological Disease, The Second Affiliated Hospital of Soochow University, Suzhou, 215123, China
| | - Wei Yang
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University; Clinical Research Center of Neurological Disease, The Second Affiliated Hospital of Soochow University, Suzhou, 215123, China
| | - Yunpeng Zhang
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu, 215163, China
| | - Yingnan Nie
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, 200433, China
| | - Mingming Hao
- i-Lab, Key Laboratory of Multifunctional Nanomaterials and Smart Systems, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou, Jiangsu, 215123, China
- Ningbo Medical Centre Lihuili Hospital, Ningbo, Zhejiang, 315048, China
| | - Pengcheng Wang
- Institutes of Biology and Medical Sciences, Soochow University, Suzhou, Jiangsu, 215123, China
| | - Hang Ruan
- Institutes of Biology and Medical Sciences, Soochow University, Suzhou, Jiangsu, 215123, China
| | - Ting Zhang
- i-Lab, Key Laboratory of Multifunctional Nanomaterials and Smart Systems, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou, Jiangsu, 215123, China
| | - Shouyan Wang
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, 200433, China
| | - Yaobo Liu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University; Clinical Research Center of Neurological Disease, The Second Affiliated Hospital of Soochow University, Suzhou, 215123, China.
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong, 226001, China.
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Lin X, Wang X, Zhang Y, Chu G, Liang J, Zhang B, Lu Y, Steward O, Luo J. Synergistic effect of chemogenetic activation of corticospinal motoneurons and physical exercise in promoting functional recovery after spinal cord injury. Exp Neurol 2023; 370:114549. [PMID: 37774765 DOI: 10.1016/j.expneurol.2023.114549] [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: 03/19/2023] [Revised: 09/06/2023] [Accepted: 09/25/2023] [Indexed: 10/01/2023]
Abstract
Single therapeutic interventions have not yet been successful in restoring function after spinal cord injury. Accordingly, combinatorial interventions targeting multiple factors may hold greater promise for achieving maximal functional recovery. In this study, we applied a combinatorial approach of chronic chemogenetic neuronal activation and physical exercise including treadmill running and forelimb training tasks to promote functional recovery. In a mouse model of cervical (C5) dorsal hemisection of the spinal cord, which transects almost all descending corticospinal tract axons, combining selective activation of corticospinal motoneurons (CMNs) by intersectional chemogenetics with physical exercise significantly promoted functional recovery evaluated by the grid walking test, grid hanging test, rotarod test, and single pellet-reaching tasks. Electromyography and histological analysis showed increased activation of forelimb muscles via chemogenetic stimuli, and a greater density of vGlut1+ innervation in spinal cord grey matter rostral to the injury, suggesting enhanced neuroplasticity and connectivity. Combined therapy also enhanced activation of mTOR signaling and reduced apoptosis in spinal motoneurons, Counts revealed increased numbers of detectable choline acetyltransferase-positive motoneurons in the ventral horn. Taken together, the findings from this study validate a novel combinatorial approach to enhance motor function after spinal cord injury.
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Affiliation(s)
- Xueling Lin
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xiuping Wang
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Yuejin Zhang
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Guangpin Chu
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Jingwen Liang
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Bin Zhang
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Yisheng Lu
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
| | - Oswald Steward
- Reeve-Irvine Research Center, University of California Irvine School of Medicine, USA; Department of Anatomy & Neurobiology, University of California Irvine School of Medicine, USA; Department of Neurobiology & Behavior, University of California Irvine, USA; Department of Neurosurgery, University of California Irvine School of Medicine, USA.
| | - Juan Luo
- Department of Physiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
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Dougherty KJ. Distinguishing subtypes of spinal locomotor neurons to inform circuit function and dysfunction. Curr Opin Neurobiol 2023; 82:102763. [PMID: 37611531 PMCID: PMC10578609 DOI: 10.1016/j.conb.2023.102763] [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: 05/10/2023] [Revised: 06/30/2023] [Accepted: 07/22/2023] [Indexed: 08/25/2023]
Abstract
Locomotion is a complex motor task executed by spinal neurons. Given the diversity of spinal cord neurons, linking neuronal cell type to function is a challenge. Molecular identification of broad spinal interneuronal classes provided a great advance. Recent studies have used other classifiers, including location, electrophysiological properties, and connectivity, in addition to gene profiling, to narrow the acuity with which groups of neurons can be related to specific functions. However, there are also functional populations without a clear identifier, as exemplified by rhythm generating neurons. Other considerations, including experience or plasticity, add a layer of complexity to the definition of functional subpopulations of spinal neurons, but spinal cord injury may provide insight.
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Affiliation(s)
- Kimberly J Dougherty
- Marion Murray Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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5
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Punjani N, Deska-Gauthier D, Hachem LD, Abramian M, Fehlings MG. Neuroplasticity and regeneration after spinal cord injury. NORTH AMERICAN SPINE SOCIETY JOURNAL 2023; 15:100235. [PMID: 37416090 PMCID: PMC10320621 DOI: 10.1016/j.xnsj.2023.100235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 06/05/2023] [Accepted: 06/05/2023] [Indexed: 07/08/2023]
Abstract
Spinal cord injury (SCI) is a debilitating condition with significant personal, societal, and economic burden. The highest proportion of traumatic injuries occur at the cervical level, which results in severe sensorimotor and autonomic deficits. Following the initial physical damage associated with traumatic injuries, secondary pro-inflammatory, excitotoxic, and ischemic cascades are initiated further contributing to neuronal and glial cell death. Additionally, emerging evidence has begun to reveal that spinal interneurons undergo subtype specific neuroplastic circuit rearrangements in the weeks to months following SCI, contributing to or hindering functional recovery. The current therapeutic guidelines and standards of care for SCI patients include early surgery, hemodynamic regulation, and rehabilitation. Additionally, preclinical work and ongoing clinical trials have begun exploring neuroregenerative strategies utilizing endogenous neural stem/progenitor cells, stem cell transplantation, combinatorial approaches, and direct cell reprogramming. This review will focus on emerging cellular and noncellular regenerative therapies with an overview of the current available strategies, the role of interneurons in plasticity, and the exciting research avenues enhancing tissue repair following SCI.
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Affiliation(s)
- Nayaab Punjani
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Dylan Deska-Gauthier
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Laureen D. Hachem
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Department of Surgery, Division of Neurosurgery and Spine Program, University of Toronto, Toronto, ON, Canada
| | - Madlene Abramian
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Michael G. Fehlings
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Department of Surgery, Division of Neurosurgery and Spine Program, University of Toronto, Toronto, ON, Canada
- Division of Neurosurgery, Krembil Neuroscience Centre, Toronto Western Hospital, University Health Network, Toronto, ON, Canada
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6
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Goltash S, Stevens SJ, Topcu E, Bui TV. Changes in synaptic inputs to dI3 INs and MNs after complete transection in adult mice. Front Neural Circuits 2023; 17:1176310. [PMID: 37476398 PMCID: PMC10354275 DOI: 10.3389/fncir.2023.1176310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 06/21/2023] [Indexed: 07/22/2023] Open
Abstract
Introduction Spinal cord injury (SCI) is a debilitating condition that disrupts the communication between the brain and the spinal cord. Several studies have sought to determine how to revive dormant spinal circuits caudal to the lesion to restore movements in paralyzed patients. So far, recovery levels in human patients have been modest at best. In contrast, animal models of SCI exhibit more recovery of lost function. Previous work from our lab has identified dI3 interneurons as a spinal neuron population central to the recovery of locomotor function in spinalized mice. We seek to determine the changes in the circuitry of dI3 interneurons and motoneurons following SCI in adult mice. Methods After a complete transection of the spinal cord at T9-T11 level in transgenic Isl1:YFP mice and subsequent treadmill training at various time points of recovery following surgery, we examined changes in three key circuits involving dI3 interneurons and motoneurons: (1) Sensory inputs from proprioceptive and cutaneous afferents, (2) Presynaptic inhibition of sensory inputs, and (3) Central excitatory glutamatergic synapses from spinal neurons onto dI3 INs and motoneurons. Furthermore, we examined the possible role of treadmill training on changes in synaptic connectivity to dI3 interneurons and motoneurons. Results Our data suggests that VGLUT1+ inputs to dI3 interneurons decrease transiently or only at later stages after injury, whereas levels of VGLUT1+ remain the same for motoneurons after injury. Levels of VGLUT2+ inputs to dI3 INs and MNs may show transient increases but fall below levels seen in sham-operated mice after a period of time. Levels of presynaptic inhibition to VGLUT1+ inputs to dI3 INs and MNs can rise shortly after SCI, but those increases do not persist. However, levels of presynaptic inhibition to VGLUT1+ inputs never fell below levels observed in sham-operated mice. For some synaptic inputs studied, levels were higher in spinal cord-injured animals that received treadmill training, but these increases were observed only at some time points. Discussion These results suggest remodeling of spinal circuits involving spinal interneurons that have previously been implicated in the recovery of locomotor function after spinal cord injury in mice.
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7
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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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8
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Kaur J, Mojumdar A. A mechanistic overview of spinal cord injury, oxidative DNA damage repair and neuroprotective therapies. Int J Neurosci 2023; 133:307-321. [PMID: 33789065 DOI: 10.1080/00207454.2021.1912040] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Despite substantial development in medical treatment strategies scientists are struggling to find a cure against spinal cord injury (SCI) which causes long term disability and paralysis. The prime rationale behind it is the enlargement of primary lesion due to an initial trauma to the spinal cord which spreads to the neighbouring spinal tissues It begins from the time of traumatic event happened and extends to hours and even days. It further causes series of biological and functional alterations such as inflammation, excitotoxicity and ischemia, and promotes secondary lesion to the cord which worsens the life of individuals affected by SCI. Oxidative DNA damage is a stern consequence of oxidative stress linked with secondary injury causes oxidative base alterations and strand breaks, which provokes cell death in neurons. It is implausible to stop primary damage however it is credible to halt the secondary lesion and improve the quality of the patient's life to some extent. Therefore it is crucial to understand the hidden perspectives of cell and molecular biology affecting the pathophysiology of SCI. Thus the focus of the review is to connect the missing links and shed light on the oxidative DNA damages and the functional repair mechanisms, as a consequence of the injury in neurons. The review will also probe the significance of neuroprotective strategies in the present scenario. HIGHLIGHTSSpinal cord injury, a pernicious condition, causes excitotoxicity and ischemia, ultimately leading to cell death.Oxidative DNA damage is a consequence of oxidative stress linked with secondary injury, provoking cell death in neurons.Base excision repair (BER) is one of the major repair pathways that plays a crucial role in repairing oxidative DNA damages.Neuroprotective therapies curbing SCI and boosting BER include the usage of pharmacological drugs and other approaches.
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Affiliation(s)
- Jaspreet Kaur
- Department of Neuroscience, University of Copenhagen, Copenhagen N, Denmark
| | - Aditya Mojumdar
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada
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9
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Anderson MA, Squair JW, Gautier M, Hutson TH, Kathe C, Barraud Q, Bloch J, Courtine G. Natural and targeted circuit reorganization after spinal cord injury. Nat Neurosci 2022; 25:1584-1596. [PMID: 36396975 DOI: 10.1038/s41593-022-01196-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 10/05/2022] [Indexed: 11/18/2022]
Abstract
A spinal cord injury disrupts communication between the brain and the circuits in the spinal cord that regulate neurological functions. The consequences are permanent paralysis, loss of sensation and debilitating dysautonomia. However, the majority of circuits located above and below the injury remain anatomically intact, and these circuits can reorganize naturally to improve function. In addition, various neuromodulation therapies have tapped into these processes to further augment recovery. Emerging research is illuminating the requirements to reconstitute damaged circuits. Here, we summarize these natural and targeted reorganizations of circuits after a spinal cord injury. We also advocate for new concepts of reorganizing circuits informed by multi-omic single-cell atlases of recovery from injury. These atlases will uncover the molecular logic that governs the selection of 'recovery-organizing' neuronal subpopulations, and are poised to herald a new era in spinal cord medicine.
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Affiliation(s)
- Mark A Anderson
- NeuroX Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.,Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.,Defitech Center for Interventional Neurotherapies (NeuroRestore), EPFL/CHUV/UNIL, Lausanne, Switzerland.,Wyss Center for Bio and Neuroengineering, Geneva, Switzerland
| | - Jordan W Squair
- NeuroX Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.,Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.,Defitech Center for Interventional Neurotherapies (NeuroRestore), EPFL/CHUV/UNIL, Lausanne, Switzerland
| | - Matthieu Gautier
- NeuroX Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.,Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.,Defitech Center for Interventional Neurotherapies (NeuroRestore), EPFL/CHUV/UNIL, Lausanne, Switzerland
| | - Thomas H Hutson
- NeuroX Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.,Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.,Defitech Center for Interventional Neurotherapies (NeuroRestore), EPFL/CHUV/UNIL, Lausanne, Switzerland.,Wyss Center for Bio and Neuroengineering, Geneva, Switzerland
| | - Claudia Kathe
- NeuroX Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.,Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.,Defitech Center for Interventional Neurotherapies (NeuroRestore), EPFL/CHUV/UNIL, Lausanne, Switzerland
| | - Quentin Barraud
- NeuroX Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.,Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.,Defitech Center for Interventional Neurotherapies (NeuroRestore), EPFL/CHUV/UNIL, Lausanne, Switzerland
| | - Jocelyne Bloch
- NeuroX Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.,Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.,Defitech Center for Interventional Neurotherapies (NeuroRestore), EPFL/CHUV/UNIL, Lausanne, Switzerland
| | - Grégoire Courtine
- NeuroX Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland. .,Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland. .,Defitech Center for Interventional Neurotherapies (NeuroRestore), EPFL/CHUV/UNIL, Lausanne, Switzerland.
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10
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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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11
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Eisdorfer JT, Sobotka-Briner H, Schramfield S, Moukarzel G, Chen J, Campion TJ, Smit R, Rauscher BC, Lemay MA, Smith GM, Spence AJ. Chemogenetic modulation of sensory afferents induces locomotor changes and plasticity after spinal cord injury. Front Mol Neurosci 2022; 15:872634. [PMID: 36090254 PMCID: PMC9461563 DOI: 10.3389/fnmol.2022.872634] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 07/26/2022] [Indexed: 12/12/2022] Open
Abstract
Neuromodulatory therapies for spinal cord injury (SCI) such as electrical epidural stimulation (EES) are increasingly effective at improving patient outcomes. These improvements are thought to be due, at least in part, to plasticity in neuronal circuits. Precisely which circuits are influenced and which afferent classes are most effective in stimulating change remain important open questions. Genetic tools, such as Designer Receptors Exclusively Activated by Designer Drugs (DREADDs), support targeted and reversible neuromodulation as well as histological characterization of manipulated neurons. We therefore transduced and activated lumbar large diameter peripheral afferents with excitatory (hM3Dq) DREADDs, in a manner analogous to EES, in a rat hemisection model, to begin to trace plasticity and observe concomitant locomotor changes. Chronic DREADDs activation, coupled with thrice weekly treadmill training, was observed to increase afferent fluorescent labeling within motor pools and Clarke's column when compared to control animals. This plasticity may underlie kinematic differences that we observed across stages of recovery, including an increased and less variable hindquarters height in DREADDs animals, shorter step durations, a more flexed ankle joint early in recovery, a less variable ankle joint angle in swing phase, but a more variable hip joint angle. Withdrawal of DREADDs agonist, clozapine-N-oxide (CNO) left these kinematic differences largely unaffected; suggesting that DREADDs activation is not necessary for them later in recovery. However, we observed an intermittent “buckling” phenomenon in DREADDs animals without CNO activation, that did not occur with CNO re-administration. Future studies could use more refined genetic targeted of specific afferent classes, and utilize muscle recordings to find where afferent modulation is most influential in altering motor output.
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Affiliation(s)
- Jaclyn T. Eisdorfer
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, United States
| | - Hannah Sobotka-Briner
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - Susan Schramfield
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - George Moukarzel
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - Jie Chen
- Department of Neuroscience, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Thomas J. Campion
- Department of Neuroscience, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Rupert Smit
- Department of Neuroscience, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Bradley C. Rauscher
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - Michel A. Lemay
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - George M. Smith
- Department of Neuroscience, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Andrew J. Spence
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
- *Correspondence: Andrew J. Spence
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12
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Neurotransmitter phenotype switching by spinal excitatory interneurons regulates locomotor recovery after spinal cord injury. Nat Neurosci 2022; 25:617-629. [PMID: 35524138 PMCID: PMC9076533 DOI: 10.1038/s41593-022-01067-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 03/29/2022] [Indexed: 11/08/2022]
Abstract
Severe spinal cord injury in adults leads to irreversible paralysis below the lesion. However, adult rodents that received a complete thoracic lesion just after birth demonstrate proficient hindlimb locomotion without input from the brain. How the spinal cord achieves such striking plasticity remains unknown. In this study, we found that adult spinal cord injury prompts neurotransmitter switching of spatially defined excitatory interneurons to an inhibitory phenotype, promoting inhibition at synapses contacting motor neurons. In contrast, neonatal spinal cord injury maintains the excitatory phenotype of glutamatergic interneurons and causes synaptic sprouting to facilitate excitation. Furthermore, genetic manipulation to mimic the inhibitory phenotype observed in excitatory interneurons after adult spinal cord injury abrogates autonomous locomotor functionality in neonatally injured mice. In comparison, attenuating this inhibitory phenotype improves locomotor capacity after adult injury. Together, these data demonstrate that neurotransmitter phenotype of defined excitatory interneurons steers locomotor recovery after spinal cord injury.
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13
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Progression in translational research on spinal cord injury based on microenvironment imbalance. Bone Res 2022; 10:35. [PMID: 35396505 PMCID: PMC8993811 DOI: 10.1038/s41413-022-00199-9] [Citation(s) in RCA: 63] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Revised: 11/14/2021] [Accepted: 12/22/2021] [Indexed: 02/07/2023] Open
Abstract
Spinal cord injury (SCI) leads to loss of motor and sensory function below the injury level and imposes a considerable burden on patients, families, and society. Repair of the injured spinal cord has been recognized as a global medical challenge for many years. Significant progress has been made in research on the pathological mechanism of spinal cord injury. In particular, with the development of gene regulation, cell sequencing, and cell tracing technologies, in-depth explorations of the SCI microenvironment have become more feasible. However, translational studies related to repair of the injured spinal cord have not yielded significant results. This review summarizes the latest research progress on two aspects of SCI pathology: intraneuronal microenvironment imbalance and regenerative microenvironment imbalance. We also review repair strategies for the injured spinal cord based on microenvironment imbalance, including medications, cell transplantation, exosomes, tissue engineering, cell reprogramming, and rehabilitation. The current state of translational research on SCI and future directions are also discussed. The development of a combined, precise, and multitemporal strategy for repairing the injured spinal cord is a potential future direction.
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The Role of Muscle Spindle Feedback in the Guidance of Hindlimb Movement by the Ipsilateral Forelimb during Locomotion in Mice. eNeuro 2021; 8:ENEURO.0432-21.2021. [PMID: 34764190 PMCID: PMC8641919 DOI: 10.1523/eneuro.0432-21.2021] [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: 10/13/2021] [Revised: 10/14/2021] [Accepted: 11/02/2021] [Indexed: 11/21/2022] Open
Abstract
Safe and efficient locomotion relies on placing the foot on a reliable surface at the end of each leg swing movement. Visual information has been shown to be important for determining the location of foot placement in humans during walking when precision is required. Yet in quadrupedal animals where the hindlimbs are outside of the visual field, such as in mice, the mechanisms by which precise foot placement is achieved remain unclear. Here we show that the placement of the hindlimb paw is determined by the position of the forelimb paw during normal locomotion and in the presence of perturbations. When a perturbation elicits a stumbling corrective reaction, we found that the forelimb paw shifts posteriorly relative to body at the end of stance, and this spatial shift is echoed in hindlimb paw placement at the end of the swing movement. Using a mutant mouse line in which muscle spindle feedback is selectively removed, we show that this posterior shift of paw placement is dependent on muscle spindle feedback in the hindlimb but not in the forelimb. These findings uncover a neuronal mechanism that is independent of vision to ensure safe locomotion during perturbation. This mechanism adds to our general knowledge of how the nervous system controls targeted limb movements and could inform the development of autonomous walking machines.
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15
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Zhang H, Liu Y, Zhou K, Wei W, Liu Y. Restoring Sensorimotor Function Through Neuromodulation After Spinal Cord Injury: Progress and Remaining Challenges. Front Neurosci 2021; 15:749465. [PMID: 34720867 PMCID: PMC8551759 DOI: 10.3389/fnins.2021.749465] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 09/13/2021] [Indexed: 12/27/2022] Open
Abstract
Spinal cord injury (SCI) is a major disability that results in motor and sensory impairment and extensive complications for the affected individuals which not only affect the quality of life of the patients but also result in a heavy burden for their families and the health care system. Although there are few clinically effective treatments for SCI, research over the past few decades has resulted in several novel treatment strategies which are related to neuromodulation. Neuromodulation-the use of neuromodulators, electrical stimulation or optogenetics to modulate neuronal activity-can substantially promote the recovery of sensorimotor function after SCI. Recent studies have shown that neuromodulation, in combination with other technologies, can allow paralyzed patients to carry out intentional, controlled movement, and promote sensory recovery. Although such treatments hold promise for completely overcoming SCI, the mechanisms by which neuromodulation has this effect have been difficult to determine. Here we review recent progress relative to electrical neuromodulation and optogenetics neuromodulation. We also examine potential mechanisms by which these methods may restore sensorimotor function. We then highlight the strengths of these approaches and remaining challenges with respect to its application.
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Affiliation(s)
- Hui Zhang
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University, Suzhou, China
| | - Yaping Liu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University, Suzhou, China
| | - Kai Zhou
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University, Suzhou, China
| | - Wei Wei
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University, Suzhou, China
| | - Yaobo Liu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University, Suzhou, China
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16
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Garcia-Ramirez DL, Ha NT, Bibu S, Stachowski NJ, Dougherty KJ. Spinal Cord Injury Alters Spinal Shox2 Interneurons by Enhancing Excitatory Synaptic Input and Serotonergic Modulation While Maintaining Intrinsic Properties in Mouse. J Neurosci 2021; 41:5833-5848. [PMID: 34006587 PMCID: PMC8265802 DOI: 10.1523/jneurosci.1576-20.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 05/03/2021] [Accepted: 05/05/2021] [Indexed: 12/11/2022] Open
Abstract
Neural circuitry generating locomotor rhythm and pattern is located in the spinal cord. Most spinal cord injuries (SCIs) occur above the level of spinal locomotor neurons; therefore, these circuits are a target for improving motor function after SCI. Despite being relatively intact below the injury, locomotor circuitry undergoes substantial plasticity with the loss of descending control. Information regarding cell type-specific plasticity within locomotor circuits is limited. Shox2 interneurons (INs) have been linked to locomotor rhythm generation and patterning, making them a potential therapeutic target for the restoration of locomotion after SCI. The goal of the present study was to identify SCI-induced plasticity at the level of Shox2 INs in a complete thoracic transection model in adult male and female mice. Whole-cell patch-clamp recordings of Shox2 INs revealed minimal changes in intrinsic excitability properties after SCI. However, afferent stimulation resulted in mixed excitatory and inhibitory input to Shox2 INs in uninjured mice which became predominantly excitatory after SCI. Shox2 INs were differentially modulated by serotonin (5-HT) in a concentration-dependent manner in uninjured conditions but following SCI, 5-HT predominantly depolarized Shox2 INs. 5-HT7 receptors mediated excitatory effects on Shox2 INs from both uninjured and SCI mice, but activation of 5-HT2B/2C receptors enhanced excitability of Shox2 INs only after SCI. Overall, SCI alters sensory afferent input pathways to Shox2 INs and 5-HT modulation of Shox2 INs to enhance excitatory responses. Our findings provide relevant information regarding the locomotor circuitry response to SCI that could benefit strategies to improve locomotion after SCI.SIGNIFICANCE STATEMENT Current therapies to gain locomotor control after spinal cord injury (SCI) target spinal locomotor circuitry. Improvements in therapeutic strategies will require a better understanding of the SCI-induced plasticity within specific locomotor elements and their controllers, including sensory afferents and serotonergic modulation. Here, we demonstrate that excitability and intrinsic properties of Shox2 interneurons, which contribute to the generation of the locomotor rhythm and pattering, remain intact after SCI. However, SCI induces plasticity in both sensory afferent pathways and serotonergic modulation, enhancing the activation and excitation of Shox2 interneurons. Our findings will impact future strategies looking to harness these changes with the ultimate goal of restoring functional locomotion after SCI.
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Affiliation(s)
- D Leonardo Garcia-Ramirez
- Marion Murray Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
| | - Ngoc T Ha
- Marion Murray Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
| | - Steve Bibu
- Marion Murray Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
| | - Nicholas J Stachowski
- Marion Murray Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
| | - Kimberly J Dougherty
- Marion Murray Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
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17
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Lalonde NR, Bui TV. Do spinal circuits still require gating of sensory information by presynaptic inhibition after spinal cord injury? CURRENT OPINION IN PHYSIOLOGY 2021. [DOI: 10.1016/j.cophys.2020.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Eisdorfer JT, Smit RD, Keefe KM, Lemay MA, Smith GM, Spence AJ. Epidural Electrical Stimulation: A Review of Plasticity Mechanisms That Are Hypothesized to Underlie Enhanced Recovery From Spinal Cord Injury With Stimulation. Front Mol Neurosci 2020; 13:163. [PMID: 33013317 PMCID: PMC7497436 DOI: 10.3389/fnmol.2020.00163] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 08/07/2020] [Indexed: 12/17/2022] Open
Abstract
Spinal cord injury (SCI) often results in life-long sensorimotor impairment. Spontaneous recovery from SCI is limited, as supraspinal fibers cannot spontaneously regenerate to form functional networks below the level of injury. Despite this, animal models and humans exhibit many motor behaviors indicative of recovery when electrical stimulation is applied epidurally to the dorsal aspect of the lumbar spinal cord. In 1976, epidural stimulation was introduced to alleviate spasticity in Multiple Sclerosis. Since then, epidural electrical stimulation (EES) has been demonstrated to improve voluntary mobility across the knee and/or ankle in several SCI patients, highlighting its utility in enhancing motor activation. The mechanisms that EES induces to drive these improvements in sensorimotor function remain largely unknown. In this review, we discuss several sensorimotor plasticity mechanisms that we hypothesize may enable epidural stimulation to promote recovery, including changes in local lumbar circuitry, propriospinal interneurons, and the internal model. Finally, we discuss genetic tools for afferent modulation as an emerging method to facilitate the search for the mechanisms of action.
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Affiliation(s)
- Jaclyn T. Eisdorfer
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - Rupert D. Smit
- Department of Neuroscience, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Kathleen M. Keefe
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - Michel A. Lemay
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - George M. Smith
- Department of Neuroscience, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Andrew J. Spence
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
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19
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Akay T. Sensory Feedback Control of Locomotor Pattern Generation in Cats and Mice. Neuroscience 2020; 450:161-167. [PMID: 32422335 DOI: 10.1016/j.neuroscience.2020.05.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/31/2020] [Accepted: 05/05/2020] [Indexed: 01/02/2023]
Abstract
Traditionally, research aimed at the understanding of the sensory control of terrestrial mammalian locomotion has focused on cats as the animal model. But advances in molecular genetics and new methods to record movement in small animals have moved mice into the forefront of locomotor research. In this review article, I will first give an overview of what is known about sensory feedback control of locomotion, mainly emerged from experiments performed on cats. This overview will not be an exhaustive overview, but will rather aim to give a broad picture of what has been learned about the sensory control of locomotion using cats as the animal model. I will then give a brief summary of how the mouse is adding to these insights.
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Affiliation(s)
- Turgay Akay
- Dalhousie University, Dept. of Medical Neuroscience, Atlantic Mobility Action Project, Brain Repair Center, Halifax, NS, Canada.
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20
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Harnie J, Doelman A, de Vette E, Audet J, Desrochers E, Gaudreault N, Frigon A. The recovery of standing and locomotion after spinal cord injury does not require task-specific training. eLife 2019; 8:50134. [PMID: 31825306 PMCID: PMC6924957 DOI: 10.7554/elife.50134] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 12/08/2019] [Indexed: 12/20/2022] Open
Abstract
After complete spinal cord injury, mammals, including mice, rats and cats, recover hindlimb locomotion with treadmill training. The premise is that sensory cues consistent with locomotion reorganize spinal sensorimotor circuits. Here, we show that hindlimb standing and locomotion recover after spinal transection in cats without task-specific training. Spinal-transected cats recovered full weight bearing standing and locomotion after five weeks of rhythmic manual stimulation of triceps surae muscles (non-specific training) and without any intervention. Moreover, cats modulated locomotor speed and performed split-belt locomotion six weeks after spinal transection, functions that were not trained or tested in the weeks prior. This indicates that spinal networks controlling standing and locomotion and their interactions with sensory feedback from the limbs remain largely intact after complete spinal cord injury. We conclude that standing and locomotor recovery is due to the return of neuronal excitability within spinal sensorimotor circuits that do not require task-specific activity-dependent plasticity.
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Affiliation(s)
- Jonathan Harnie
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Canada
| | - Adam Doelman
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Canada
| | - Emmanuelle de Vette
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Canada
| | - Johannie Audet
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Canada
| | - Etienne Desrochers
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Canada
| | - Nathaly Gaudreault
- School of Rehabilitation, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Canada
| | - Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Canada
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21
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Laliberte AM, Goltash S, Lalonde NR, Bui TV. Propriospinal Neurons: Essential Elements of Locomotor Control in the Intact and Possibly the Injured Spinal Cord. Front Cell Neurosci 2019; 13:512. [PMID: 31798419 PMCID: PMC6874159 DOI: 10.3389/fncel.2019.00512] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 10/29/2019] [Indexed: 12/22/2022] Open
Abstract
Propriospinal interneurons (INs) communicate information over short and long distances within the spinal cord. They act to coordinate different parts of the body by linking motor circuits that control muscles across the forelimbs, trunk, and hindlimbs. Their role in coordinating locomotor circuits near and far may be invaluable to the recovery of locomotor function lost due to injury to the spinal cord where the flow of motor commands from the brain and brainstem to spinal motor circuits is disrupted. The formation and activation of circuits established by spared propriospinal INs may promote the re-emergence of locomotion. In light of progress made in animal models of spinal cord injury (SCI) and in human patients, we discuss the role of propriospinal INs in the intact spinal cord and describe recent studies investigating the assembly and/or activation of propriospinal circuits to promote recovery of locomotion following SCI.
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Affiliation(s)
- Alex M Laliberte
- Department of Biology, Faculty of Science, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
| | - Sara Goltash
- Department of Biology, Faculty of Science, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
| | - Nicolas R Lalonde
- Department of Biology, Faculty of Science, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
| | - Tuan Vu Bui
- Department of Biology, Faculty of Science, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
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22
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Grillner S, El Manira A. Current Principles of Motor Control, with Special Reference to Vertebrate Locomotion. Physiol Rev 2019; 100:271-320. [PMID: 31512990 DOI: 10.1152/physrev.00015.2019] [Citation(s) in RCA: 220] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vertebrate control of locomotion involves all levels of the nervous system from cortex to the spinal cord. Here, we aim to cover all main aspects of this complex behavior, from the operation of the microcircuits in the spinal cord to the systems and behavioral levels and extend from mammalian locomotion to the basic undulatory movements of lamprey and fish. The cellular basis of propulsion represents the core of the control system, and it involves the spinal central pattern generator networks (CPGs) controlling the timing of different muscles, the sensory compensation for perturbations, and the brain stem command systems controlling the level of activity of the CPGs and the speed of locomotion. The forebrain and in particular the basal ganglia are involved in determining which motor programs should be recruited at a given point of time and can both initiate and stop locomotor activity. The propulsive control system needs to be integrated with the postural control system to maintain body orientation. Moreover, the locomotor movements need to be steered so that the subject approaches the goal of the locomotor episode, or avoids colliding with elements in the environment or simply escapes at high speed. These different aspects will all be covered in the review.
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Affiliation(s)
- Sten Grillner
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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23
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Steuer I, Guertin PA. Central pattern generators in the brainstem and spinal cord: an overview of basic principles, similarities and differences. Rev Neurosci 2019; 30:107-164. [PMID: 30543520 DOI: 10.1515/revneuro-2017-0102] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 03/30/2018] [Indexed: 12/11/2022]
Abstract
Central pattern generators (CPGs) are generally defined as networks of neurons capable of enabling the production of central commands, specifically controlling stereotyped, rhythmic motor behaviors. Several CPGs localized in brainstem and spinal cord areas have been shown to underlie the expression of complex behaviors such as deglutition, mastication, respiration, defecation, micturition, ejaculation, and locomotion. Their pivotal roles have clearly been demonstrated although their organization and cellular properties remain incompletely characterized. In recent years, insightful findings about CPGs have been made mainly because (1) several complementary animal models were developed; (2) these models enabled a wide variety of techniques to be used and, hence, a plethora of characteristics to be discovered; and (3) organizations, functions, and cell properties across all models and species studied thus far were generally found to be well-preserved phylogenetically. This article aims at providing an overview for non-experts of the most important findings made on CPGs in in vivo animal models, in vitro preparations from invertebrate and vertebrate species as well as in primates. Data about CPG functions, adaptation, organization, and cellular properties will be summarized with a special attention paid to the network for locomotion given its advanced level of characterization compared with some of the other CPGs. Similarities and differences between these networks will also be highlighted.
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Affiliation(s)
- Inge Steuer
- Neuroscience Unit, Laval University Medical Center (CHUL - CHU de Québec), 2705 Laurier Blvd, Quebec City, Quebec G1V 4G2, Canada
| | - Pierre A Guertin
- Neuroscience Unit, Laval University Medical Center (CHUL - CHU de Québec), 2705 Laurier Blvd, Quebec City, Quebec G1V 4G2, Canada
- Faculty of Medicine, Department of Psychiatry and Neurosciences, Laval University, Quebec City, Quebec G1V 0A6, Canada
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24
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Santuz A, Akay T, Mayer WP, Wells TL, Schroll A, Arampatzis A. Modular organization of murine locomotor pattern in the presence and absence of sensory feedback from muscle spindles. J Physiol 2019; 597:3147-3165. [DOI: 10.1113/jp277515] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 03/15/2019] [Indexed: 11/08/2022] Open
Affiliation(s)
- Alessandro Santuz
- Department of Training and Movement SciencesHumboldt‐Universität zu Berlin 10115 Berlin Germany
- Berlin School of Movement ScienceHumboldt‐Universität zu Berlin 10115 Berlin Germany
- Atlantic Mobility Action ProjectBrain Repair CentreDepartment of Medical NeuroscienceDalhousie University Halifax Nova Scotia B3H 4R2 Canada
| | - Turgay Akay
- Atlantic Mobility Action ProjectBrain Repair CentreDepartment of Medical NeuroscienceDalhousie University Halifax Nova Scotia B3H 4R2 Canada
| | - William P. Mayer
- Atlantic Mobility Action ProjectBrain Repair CentreDepartment of Medical NeuroscienceDalhousie University Halifax Nova Scotia B3H 4R2 Canada
- Department of MorphologyFederal University of Espirito Santo Vitoria CEP 29040–090 Brazil
| | - Tyler L. Wells
- Atlantic Mobility Action ProjectBrain Repair CentreDepartment of Medical NeuroscienceDalhousie University Halifax Nova Scotia B3H 4R2 Canada
| | - Arno Schroll
- Department of Training and Movement SciencesHumboldt‐Universität zu Berlin 10115 Berlin Germany
- Berlin School of Movement ScienceHumboldt‐Universität zu Berlin 10115 Berlin Germany
| | - Adamantios Arampatzis
- Department of Training and Movement SciencesHumboldt‐Universität zu Berlin 10115 Berlin Germany
- Berlin School of Movement ScienceHumboldt‐Universität zu Berlin 10115 Berlin Germany
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25
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Dougherty KJ, Ha NT. The rhythm section: An update on spinal interneurons setting the beat for mammalian locomotion. CURRENT OPINION IN PHYSIOLOGY 2019; 8:84-93. [PMID: 31179403 PMCID: PMC6550992 DOI: 10.1016/j.cophys.2019.01.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
To initiate and support locomotion, rhythm generating neurons in the spinal central pattern generator convert descending input into a rhythmic signal which is conveyed to downstream neurons, leading to the recruitment of motor neurons and activation of muscles. Although two genetically-defined neuronal populations have been linked to rhythm generation, a single all-inclusive rhythm generating population has yet to be identified. Here, we consolidate recent work aimed at identifying rhythm generating neurons, summarize the evidence for the involvement of two neuronal populations in rhythm generation, describe the challenges in identifying a marker for rhythm generating neurons, and discuss potential directions to take in integrating spinal rhythm generating neurons into recently identified speed-dependent locomotor circuits.
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Affiliation(s)
- Kimberly J. Dougherty
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
| | - Ngoc T. Ha
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
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26
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Deska-Gauthier D, Zhang Y. The functional diversity of spinal interneurons and locomotor control. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2019.01.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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27
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Koch SC. Motor task-selective spinal sensorimotor interneurons in mammalian circuits. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2019.01.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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28
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Lin S, Li Y, Lucas-Osma AM, Hari K, Stephens MJ, Singla R, Heckman CJ, Zhang Y, Fouad K, Fenrich KK, Bennett DJ. Locomotor-related V3 interneurons initiate and coordinate muscles spasms after spinal cord injury. J Neurophysiol 2019; 121:1352-1367. [PMID: 30625014 DOI: 10.1152/jn.00776.2018] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Spinal cord injury leads to a devastating loss of motor function and yet is accompanied by a paradoxical emergence of muscle spasms, which often involve complex muscle activation patterns across multiple joints, reciprocal muscle timing, and rhythmic clonus. We investigated the hypothesis that spasms are a manifestation of partially recovered function in spinal central pattern-generating (CPG) circuits that normally coordinate complex postural and locomotor functions. We focused on the commissural propriospinal V3 neurons that coordinate interlimb movements during locomotion and examined mice with a chronic spinal transection. When the V3 neurons were optogenetically activated with a light pulse, a complex coordinated pattern of motoneuron activity was evoked with reciprocal, crossed, and intersegmental activity. In these same mice, brief sensory stimulation evoked spasms with a complex pattern of activity very similar to that evoked by light, and the timing of these spasms was readily reset by activation of V3 neurons. Given that V3 neurons receive abundant sensory input, these results suggest that sensory activation of V3 neurons is alone sufficient to generate spasms. Indeed, when we silenced V3 neurons optogenetically, sensory evoked spasms were inhibited. Also, inhibiting general CPG activity by blocking N-methyl-d-aspartate (NMDA) receptors inhibited V3 evoked activity and associated spasms, whereas NMDA application did the opposite. Furthermore, overwhelming the V3 neurons with repeated optogenetic stimulation inhibited subsequent sensory evoked spasms, both in vivo and in vitro. Taken together, these results demonstrate that spasms are generated in part by sensory activation of V3 neurons and associated CPG circuits. NEW & NOTEWORTHY We investigated whether locomotor-related excitatory interneurons (V3) play a role in coordinating muscle spasm activity after spinal cord injury (SCI). Unexpectedly, we found that these neurons not only coordinate reciprocal motor activity but are critical for initiating spasms, as well. More generally, these results suggest that V3 neurons are important in initiating and coordinating motor output after SCI and thus provide a promising target for restoring residual motor function.
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Affiliation(s)
- Shihao Lin
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
| | - Yaqing Li
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
| | - Ana M Lucas-Osma
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
| | - Krishnapriya Hari
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
| | - Marilee J Stephens
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
| | - Rahul Singla
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
| | - C J Heckman
- Department of Physiology, Northwestern University, Feinberg School of Medicine , Chicago, Illinois
| | - Ying Zhang
- Department of Medical Neuroscience, Dalhousie University , Halifax, Nova Scotia , Canada
| | - Karim Fouad
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
| | - Keith K Fenrich
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
| | - David J Bennett
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, Alberta , Canada
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29
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Mayer WP, Murray AJ, Brenner-Morton S, Jessell TM, Tourtellotte WG, Akay T. Role of muscle spindle feedback in regulating muscle activity strength during walking at different speed in mice. J Neurophysiol 2018; 120:2484-2497. [PMID: 30133381 DOI: 10.1152/jn.00250.2018] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Terrestrial animals increase their walking speed by increasing the activity of the extensor muscles. However, the mechanism underlying how this speed-dependent amplitude modulation is achieved remains obscure. Previous studies have shown that group Ib afferent feedback from Golgi tendon organs that signal force is one of the major regulators of the strength of muscle activity during walking in cats and humans. In contrast, the contribution of group Ia/II afferent feedback from muscle spindle stretch receptors that signal angular displacement of leg joints is unclear. Some studies indicate that group II afferent feedback may be important for amplitude regulation in humans, but the role of muscle spindle feedback in regulation of muscle activity strength in quadrupedal animals is very poorly understood. To examine the role of feedback from muscle spindles, we combined in vivo electrophysiology and motion analysis with mouse genetics and gene delivery with adeno-associated virus. We provide evidence that proprioceptive sensory feedback from muscle spindles is important for the regulation of the muscle activity strength and speed-dependent amplitude modulation. Furthermore, our data suggest that feedback from the muscle spindles of the ankle extensor muscles, the triceps surae, is the main source for this mechanism. In contrast, muscle spindle feedback from the knee extensor muscles, the quadriceps femoris, has no influence on speed-dependent amplitude modulation. We provide evidence that proprioceptive feedback from ankle extensor muscles is critical for regulating muscle activity strength as gait speed increases. NEW & NOTEWORTHY Animals upregulate the activity of extensor muscles to increase their walking speed, but the mechanism behind this is not known. We show that this speed-dependent amplitude modulation requires proprioceptive sensory feedback from muscle spindles of ankle extensor muscle. In the absence of muscle spindle feedback, animals cannot walk at higher speeds as they can when muscle spindle feedback is present.
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Affiliation(s)
- William P Mayer
- Atlantic Mobility Action Project, Brain Repair Center, Department of Medical Neuroscience, Dalhousie University , Halifax, Nova Scotia , Canada.,Department of Morphology, Federal University of Espirito Santo , Vitoria , Brazil
| | - Andrew J Murray
- Sainsbury Wellcome Center for Neural Circuits and Behaviour, University College London , London , United Kingdom
| | - Susan Brenner-Morton
- Howard Hughes Medical Institute, Department of Neuroscience, Columbia University , New York, New York
| | - Thomas M Jessell
- Howard Hughes Medical Institute, Department of Neuroscience, Columbia University , New York, New York
| | - Warren G Tourtellotte
- Department of Pathology and Laboratory Medicine, Cedar Sinai Medical Center, West Hollywood, California
| | - Turgay Akay
- Atlantic Mobility Action Project, Brain Repair Center, Department of Medical Neuroscience, Dalhousie University , Halifax, Nova Scotia , Canada
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30
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The Neuroplastic and Therapeutic Potential of Spinal Interneurons in the Injured Spinal Cord. Trends Neurosci 2018; 41:625-639. [PMID: 30017476 DOI: 10.1016/j.tins.2018.06.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 06/06/2018] [Accepted: 06/12/2018] [Indexed: 12/25/2022]
Abstract
The central nervous system is not a static, hard-wired organ. Examples of neuroplasticity, whether at the level of the synapse, the cell, or within and between circuits, can be found during development, throughout the progression of disease, or after injury. One essential component of the molecular, anatomical, and functional changes associated with neuroplasticity is the spinal interneuron (SpIN). Here, we draw on recent multidisciplinary studies to identify and interrogate subsets of SpINs and their roles in locomotor and respiratory circuits. We highlight some of the recent progress that elucidates the importance of SpINs in circuits affected by spinal cord injury (SCI), especially those within respiratory networks; we also discuss potential ways that spinal neuroplasticity can be therapeutically harnessed for recovery.
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31
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Mayer WP, Akay T. Stumbling corrective reaction elicited by mechanical and electrical stimulation of the saphenous nerve in walking mice. ACTA ACUST UNITED AC 2018; 221:jeb.178095. [PMID: 29776999 DOI: 10.1242/jeb.178095] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 05/11/2018] [Indexed: 12/16/2022]
Abstract
The ability to walk around in a natural environment requires the capacity to cope with unexpected obstacles that may disrupt locomotion. One such mechanism is called the stumbling corrective reaction (SCR) that enables animals to step over obstacles that would otherwise disturb the progression of swing movement. Here we use in vivo motion analysis and physiological recording techniques to describe the SCR in mice. We show that SCR can be elicited consistently in mice during locomotion by inserting an obstacle along the path of leg movement during swing phase. Furthermore, we show that the same behavior can be elicited if the saphenous nerve, a cutaneous nerve that would detect contact of the leg with an object, is stimulated electrically. This suggests that cutaneous afferent feedback is sufficient to elicit SCR. We further show that the SCR is phase dependent, occurring only with stimulation during swing phase, but not during early stance. During SCR elicited by either method, the foot is lifted higher to clear the object by flexing the knee, via the semitendinosus muscle, and ankle joint, by tibialis anterior contraction. The tibialis anterior also exhibits a brief extension before flexion onset. Our data provide a detailed description of SCR in mice and will be crucial for future research that aims to identify the interneurons of the premotor network controlling SCR and its neuronal mechanisms by combining motion analysis, electrophysiology and mouse genetics.
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Affiliation(s)
- William Paganini Mayer
- Dalhousie University, Department of Medical Neuroscience, Atlantic Mobility Action Project, Brain Repair Center, Halifax, Nova Scotia, Canada B3H 4R2.,Federal University of Espirito Santo, Department of Morphology, Vitoria, Espírito Santo, Brazil 29.040-090
| | - Turgay Akay
- Dalhousie University, Department of Medical Neuroscience, Atlantic Mobility Action Project, Brain Repair Center, Halifax, Nova Scotia, Canada B3H 4R2
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32
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Klarner T, Zehr EP. Sherlock Holmes and the curious case of the human locomotor central pattern generator. J Neurophysiol 2018. [PMID: 29537920 DOI: 10.1152/jn.00554.2017] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Evidence first described in reduced animal models over 100 years ago led to deductions about the control of locomotion through spinal locomotor central pattern-generating (CPG) networks. These discoveries in nature were contemporaneous with another form of deductive reasoning found in popular culture, that of Arthur Conan Doyle's detective, Sherlock Holmes. Because the invasive methods used in reduced nonhuman animal preparations are not amenable to study in humans, we are left instead with deducing from other measures and observations. Using the deductive reasoning approach of Sherlock Holmes as a metaphor for framing research into human CPGs, we speculate and weigh the evidence that should be observable in humans based on knowledge from other species. This review summarizes indirect inference to assess "observable evidence" of pattern-generating activity that leads to the logical deduction of CPG contributions to arm and leg activity during locomotion in humans. The question of where a CPG may be housed in the human nervous system remains incompletely resolved at this time. Ongoing understanding, elaboration, and application of functioning locomotor CPGs in humans is important for gait rehabilitation strategies in those with neurological injuries.
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Affiliation(s)
- Taryn Klarner
- Rehabilitation Neuroscience Laboratory, University of Victoria , Victoria, British Columbia , Canada.,Human Discovery Science, International Collaboration on Repair Discoveries , Vancouver, British Columbia , Canada.,Centre for Biomedical Research, University of Victoria , Victoria, British Columbia , Canada
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria , Victoria, British Columbia , Canada.,Human Discovery Science, International Collaboration on Repair Discoveries , Vancouver, British Columbia , Canada.,Centre for Biomedical Research, University of Victoria , Victoria, British Columbia , Canada.,Division of Medical Sciences, University of Victoria, British Columbia, Canada
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33
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Brownstone RM, Lancelin C. Escape from homeostasis: spinal microcircuits and progression of amyotrophic lateral sclerosis. J Neurophysiol 2018; 119:1782-1794. [PMID: 29384454 PMCID: PMC6008087 DOI: 10.1152/jn.00331.2017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In amyotrophic lateral sclerosis (ALS), loss of motoneuron function leads to weakness and, ultimately, respiratory failure and death. Regardless of the initial pathogenic factors, motoneuron loss follows a specific pattern: the largest α-motoneurons die before smaller α-motoneurons, and γ-motoneurons are spared. In this article, we examine how homeostatic responses to this orderly progression could lead to local microcircuit dysfunction that in turn propagates motoneuron dysfunction and death. We first review motoneuron diversity and the principle of α-γ coactivation and then discuss two specific spinal motoneuron microcircuits: those involving proprioceptive afferents and those involving Renshaw cells. Next, we propose that the overall homeostatic response of the nervous system is aimed at maintaining force output. Thus motoneuron degeneration would lead to an increase in inputs to motoneurons, and, because of the pattern of neuronal degeneration, would result in an imbalance in local microcircuit activity that would overwhelm initial homeostatic responses. We suggest that this activity would ultimately lead to excitotoxicity of motoneurons, which would hasten the progression of disease. Finally, we propose that should this be the case, new therapies targeted toward microcircuit dysfunction could slow the course of ALS.
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Affiliation(s)
- Robert M Brownstone
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London , London , United Kingdom
| | - Camille Lancelin
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London , London , United Kingdom
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34
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Jean-Xavier C, Sharples SA, Mayr KA, Lognon AP, Whelan PJ. Retracing your footsteps: developmental insights to spinal network plasticity following injury. J Neurophysiol 2017; 119:521-536. [PMID: 29070632 DOI: 10.1152/jn.00575.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
During development of the spinal cord, a precise interaction occurs between descending projections and sensory afferents, with spinal networks that lead to expression of coordinated motor output. In the rodent, during the last embryonic week, motor output first occurs as regular bursts of spontaneous activity, progressing to stochastic patterns of episodes that express bouts of coordinated rhythmic activity perinatally. Locomotor activity becomes functionally mature in the 2nd postnatal wk and is heralded by the onset of weight-bearing locomotion on the 8th and 9th postnatal day. Concomitantly, there is a maturation of intrinsic properties and key conductances mediating plateau potentials. In this review, we discuss spinal neuronal excitability, descending modulation, and afferent modulation in the developing rodent spinal cord. In the adult, plastic mechanisms are much more constrained but become more permissive following neurotrauma, such as spinal cord injury. We discuss parallel mechanisms that contribute to maturation of network function during development to mechanisms of pathological plasticity that contribute to aberrant motor patterns, such as spasticity and clonus, which emerge following central injury.
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Affiliation(s)
- C Jean-Xavier
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
| | - S A Sharples
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Neuroscience, University of Calgary , Calgary, Alberta , Canada
| | - K A Mayr
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Neuroscience, University of Calgary , Calgary, Alberta , Canada
| | - A P Lognon
- Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
| | - P J Whelan
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
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35
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Gallego JA, Hardwick RM, Oby ER. Highlights from the 2017 meeting of the Society for Neural Control of Movement (Dublin, Ireland). Eur J Neurosci 2017; 46:2141-2148. [PMID: 28837247 DOI: 10.1111/ejn.13670] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Juan Alvaro Gallego
- Neural and Cognitive Engineering Group, Centre for Automation and Robotics CSIC-UPM, Madrid, Spain.,Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Robert M Hardwick
- Department of Neurology, Johns Hopkins University, Baltimore, MD, USA.,Movement Control and Neuroplasticity Research Group, KU Leuven, Leuven, Belgium
| | - Emily R Oby
- Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA, 15213, USA
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36
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Falgairolle M, Puhl JG, Pujala A, Liu W, O'Donovan MJ. Motoneurons regulate the central pattern generator during drug-induced locomotor-like activity in the neonatal mouse. eLife 2017; 6. [PMID: 28671548 PMCID: PMC5550280 DOI: 10.7554/elife.26622] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 06/30/2017] [Indexed: 12/17/2022] Open
Abstract
Motoneurons are traditionally viewed as the output of the spinal cord that do not influence locomotor rhythmogenesis. We assessed the role of motoneuron firing during ongoing locomotor-like activity in neonatal mice expressing archaerhopsin-3 (Arch), halorhodopsin (eNpHR), or channelrhodopsin-2 (ChR2) in Choline acetyltransferase neurons (ChAT+) or Arch in LIM-homeodomain transcription factor Isl1+ neurons. Illumination of the lumbar cord in mice expressing eNpHR or Arch in ChAT+ or Isl1+ neurons, depressed motoneuron discharge, transiently decreased the frequency, and perturbed the phasing of the locomotor-like rhythm. When the light was turned off motoneuron firing and locomotor frequency both transiently increased. These effects were not due to cholinergic neurotransmission, persisted during partial blockade of gap junctions and were mediated, in part, by AMPAergic transmission. In spinal cords expressing ChR2, illumination increased motoneuron discharge and transiently accelerated the rhythm. We conclude that motoneurons provide feedback to the central pattern generator (CPG) during drug-induced locomotor-like activity. DOI:http://dx.doi.org/10.7554/eLife.26622.001
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Affiliation(s)
- Melanie Falgairolle
- Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Joshua G Puhl
- Department of Entomology, University of Minnesota, Saint Paul, United States
| | - Avinash Pujala
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Wenfang Liu
- Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Michael J O'Donovan
- Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
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37
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Descending Systems Direct Development of Key Spinal Motor Circuits. J Neurosci 2017; 37:6372-6387. [PMID: 28576940 DOI: 10.1523/jneurosci.0149-17.2017] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 05/10/2017] [Accepted: 05/24/2017] [Indexed: 12/17/2022] Open
Abstract
The formation of mature spinal motor circuits is dependent on both activity-dependent and independent mechanisms during postnatal development. During this time, reorganization and refinement of spinal sensorimotor circuits occurs as supraspinal projections are integrated. However, specific features of postnatal spinal circuit development remain poorly understood. This study provides the first detailed characterization of rat spinal sensorimotor circuit development in the presence and absence of descending systems. We show that the development of proprioceptive afferent input to motoneurons (MNs) and Renshaw cells (RCs) is disrupted by thoracic spinal cord transection at postnatal day 5 (P5TX). P5TX also led to malformation of GABApre neuron axo-axonic contacts on Ia afferents and of the recurrent inhibitory circuit between MNs and RCs. Using a novel in situ perfused preparation for studying motor control, we show that malformation of these spinal circuits leads to hyperexcitability of the monosynaptic reflex. Our results demonstrate that removing descending input severely disrupts the development of spinal circuits and identifies key mechanisms contributing to motor dysfunction in conditions such as cerebral palsy and spinal cord injury.SIGNIFICANCE STATEMENT Acquisition of mature behavior during postnatal development correlates with the arrival and maturation of supraspinal projections to the spinal cord. However, we know little about the role that descending systems play in the maturation of spinal circuits. Here, we characterize postnatal development of key spinal microcircuits in the presence and absence of descending systems. We show that formation of these circuits is abnormal after early (postnatal day 5) removal of descending systems, inducing hyperexcitability of the monosynaptic reflex. The study is a detailed characterization of spinal circuit development elucidating how these mechanisms contribute to motor dysfunction in conditions such as cerebral palsy and spinal cord injury. Understanding these circuits is crucial to developing new therapeutics and improving existing ones in such conditions.
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