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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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Garcia-Ramirez DL, Singh S, McGrath JR, Ha NT, Dougherty KJ. Identification of adult spinal Shox2 neuronal subpopulations based on unbiased computational clustering of electrophysiological properties. Front Neural Circuits 2022; 16:957084. [PMID: 35991345 PMCID: PMC9385948 DOI: 10.3389/fncir.2022.957084] [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: 05/30/2022] [Accepted: 07/08/2022] [Indexed: 11/13/2022] Open
Abstract
Spinal cord neurons integrate sensory and descending information to produce motor output. The expression of transcription factors has been used to dissect out the neuronal components of circuits underlying behaviors. However, most of the canonical populations of interneurons are heterogeneous and require additional criteria to determine functional subpopulations. Neurons expressing the transcription factor Shox2 can be subclassified based on the co-expression of the transcription factor Chx10 and each subpopulation is proposed to have a distinct connectivity and different role in locomotion. Adult Shox2 neurons have recently been shown to be diverse based on their firing properties. Here, in order to subclassify adult mouse Shox2 neurons, we performed multiple analyses of data collected from whole-cell patch clamp recordings of visually-identified Shox2 neurons from lumbar spinal slices. A smaller set of Chx10 neurons was included in the analyses for validation. We performed k-means and hierarchical unbiased clustering approaches, considering electrophysiological variables. Unlike the categorizations by firing type, the clusters displayed electrophysiological properties that could differentiate between clusters of Shox2 neurons. The presence of clusters consisting exclusively of Shox2 neurons in both clustering techniques suggests that it is possible to distinguish Shox2+Chx10- neurons from Shox2+Chx10+ neurons by electrophysiological properties alone. Computational clusters were further validated by immunohistochemistry with accuracy in a small subset of neurons. Thus, unbiased cluster analysis using electrophysiological properties is a tool that can enhance current interneuronal subclassifications and can complement groupings based on transcription factor and molecular expression.
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Affiliation(s)
| | | | | | | | - Kimberly J. Dougherty
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States
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Li Y, Yang XY, Jin N, Zhen C, Zhu SY, Chu WY, Zhang HH, Xu AP, Wu J, Wang MY, Zheng C. Activation of M 3-AChR and IP 3/Ca 2+/PKC signaling pathways by pilocarpine increases glycine-induced currents in ventral horn neurons of the spinal cord. Neurosci Lett 2022; 782:136690. [PMID: 35598692 DOI: 10.1016/j.neulet.2022.136690] [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: 03/20/2022] [Revised: 05/14/2022] [Accepted: 05/16/2022] [Indexed: 02/05/2023]
Abstract
Our study aimed to determine the effects of pilocarpine and the mechanisms involving muscarinic acetylcholine receptors (mAChRs) on glycine receptors (GlyRs) in neurons of the spinal cord ventral horn. An enzymatic digestion combined with acute mechanical separation was applied to isolate neurons from the spinal cord ventral horn. Patch-clamp recording was then used to investigate the outcomes of pilocarpine. Our results indicate that pilocarpine increased the glycine currents in a concentration-dependent manner, which was blocked by the M3-AChR selective antagonists 4-DAMP and J104129. Pilocarpine also enhanced the glycine currents in nominally Ca2+-free extracellular solution. Conversely, the enhancement of glycine currents by pilocarpine disappeared when intracellular Ca2+ was chelated by BAPTA. Heparin and Xe-C, which are IP3 receptor antagonists, also totally abolished the pilocarpine effect. Furthermore, Bis-IV, a PKC inhibitor, eliminated the pilocarpine effect. Additionally, PMA, a PKC activator, mimicked the pilocarpine effect. These results indicate that pilocarpine may increase the glycine currents by activating the M3-AChRs and IP3/Ca2+/PKC pathways.
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Affiliation(s)
- Yan Li
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Xin-Yu Yang
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Na Jin
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Cheng Zhen
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Su-Yue Zhu
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Wan-Yu Chu
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Huan-Huan Zhang
- Psychophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Ai-Ping Xu
- Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Jie Wu
- Laboratory of Brain Function and Diseases, Shantou University Medical College, Shantou, Guangdong 515041, China
| | - Meng-Ya Wang
- Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Chao Zheng
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
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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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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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McMahon C, Kowalski DP, Krupka AJ, Lemay MA. Single-cell and ensemble activity of lumbar intermediate and ventral horn interneurons in the spinal air-stepping cat. J Neurophysiol 2022; 127:99-115. [PMID: 34851739 PMCID: PMC8721903 DOI: 10.1152/jn.00202.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 11/30/2021] [Accepted: 12/01/2021] [Indexed: 12/18/2022] Open
Abstract
We explored the relationship between population interneuronal network activation and motor output in the adult, in vivo, air-stepping, spinal cat. By simultaneously measuring the activity of large numbers of spinal interneurons, we explored ensembles of coherently firing interneurons and their relation to motor output. In addition, the networks were analyzed in relation to their spatial distribution along the lumbar enlargement for evidence of localized groups driving particular phases of the locomotor step cycle. We simultaneously recorded hindlimb EMG activity during stepping and extracellular signals from 128 channels across two polytrodes inserted within lamina V-VII of two separate lumbar segments. Results indicated that spinal interneurons participate in one of two ensembles that are highly correlated with the flexor or the extensor muscle bursts during stepping. Interestingly, less than half of the isolated single units were significantly unimodally tuned during the step cycle whereas >97% of the single units of the ensembles were significantly correlated with muscle activity. These results show the importance of population scale analysis in neural studies of behavior as there is a much greater correlation between muscle activity and ensemble firing than between muscle activity and individual neurons. Finally, we show that there is no correlation between interneurons' rostrocaudal locations within the lumbar enlargement and their preferred phase of firing or ensemble participation. These findings indicate that spinal interneurons of lamina V-VII encoding for different phases of the locomotor cycle are spread throughout the lumbar enlargement in the adult spinal cord.NEW & NOTEWORTHY We report on the ensemble organization of interneuronal activity in the spinal cord during locomotor movements and show that lumbar intermediate zone interneurons organize in two groups related to the two major phases of walking: stance and swing. Ensemble organization is also shown to better correlate with muscular output than single-cell activity, although ensemble membership does not appear to be somatotopically organized within the spinal cord.
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Affiliation(s)
- Chantal McMahon
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, Pennsylvania
| | - David P Kowalski
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, Pennsylvania
| | | | - Michel A Lemay
- Department of Bioengineering, Temple University, Philadelphia, Pennsylvania
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7
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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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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: 58] [Impact Index Per Article: 19.3] [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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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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10
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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: 15] [Impact Index Per Article: 3.8] [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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Pham BN, Luo J, Anand H, Kola O, Salcedo P, Nguyen C, Gaunt S, Zhong H, Garfinkel A, Tillakaratne N, Edgerton VR. Redundancy and multifunctionality among spinal locomotor networks. J Neurophysiol 2020; 124:1469-1479. [PMID: 32966757 DOI: 10.1152/jn.00338.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
c-Fos is used to identify system-wide neural activation with cellular resolution in vivo. However, c-Fos can only capture neural activation of one event. Targeted recombination in active populations (TRAP) allows the capture of two different c-Fos activation patterns in the same animal. So far, TRAP has only been used to examine brain circuits. This study uses TRAP to investigate spinal circuit activation during resting and stepping, giving novel insights of network activation during these events. The level of colabeled (c-Fos+ and TRAP+) neurons observed after performing two bouts of stepping suggests that there is a probabilistic-like phenomenon that can recruit many combinations of neural populations (synapses) when repetitively generating many step cycles. Between two 30-min bouts of stepping, each consisting of thousands of steps, only ∼20% of the neurons activated from the first bout of stepping were also activated by the second bout. We also show colabeling of interneurons that have been active during stepping and resting. The use of the FosTRAP methodology in the spinal cord provides a new tool to compare the engagement of different populations of spinal interneurons in vivo under different motor tasks or under different conditions.NEW & NOTEWORTHY The results are consistent with there being an extensive amount of redundancy among spinal locomotor circuits. Using the newly developed FosTRAP mouse model, only ∼20% of neurons that were active (labeled by Fos-linked tdTomato expression) during a first bout of 30-min stepping were also labeled for c-Fos during a second bout of stepping. This finding suggests variability of neural networks that enables selection of many combinations of neurons (synapses) when generating each step cycle.
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Affiliation(s)
- Bau N Pham
- Department of Bioengineering, University of California, Los Angeles, California
| | - Jiangyuan Luo
- Department of Neuroscience, University of California, Los Angeles, California
| | - Harnadar Anand
- Institute for Society and Genetics, University of California, Los Angeles, California
| | - Olivia Kola
- Department of Neuroscience, University of California, Los Angeles, California
| | - Pia Salcedo
- Department of Psychobiology, University of California, Los Angeles, California
| | - Connie Nguyen
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California
| | - Sarah Gaunt
- Department of Molecular Cellular and Developmental Biology, University of California, Los Angeles, California
| | - Hui Zhong
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California
| | - Alan Garfinkel
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California
| | - Niranjala Tillakaratne
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California.,Brain Research Institute, University of California, Los Angeles, California
| | - V Reggie Edgerton
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California.,Brain Research Institute, University of California, Los Angeles, California.,Department of Neurobiology, University of California, Los Angeles, California.,Department of Neurosurgery, University of California, Los Angeles, California.,Institut Guttmann, Hospital de Neurorehabilitació, Universitat Autònoma de Barcelona, Badalona, Spain.,Centre for Neuroscience and Regenerative Medicine, Faculty of Science, University of Technology Sydney, Ultimo, Australia
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12
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Opris I, Dai X, Johnson DMG, Sanchez FJ, Villamil LM, Xie S, Lee-Hauser CR, Chang S, Jordan LM, Noga BR. Activation of Brainstem Neurons During Mesencephalic Locomotor Region-Evoked Locomotion in the Cat. Front Syst Neurosci 2019; 13:69. [PMID: 31798423 PMCID: PMC6868058 DOI: 10.3389/fnsys.2019.00069] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/31/2019] [Indexed: 12/26/2022] Open
Abstract
The distribution of locomotor-activated neurons in the brainstem of the cat was studied by c-Fos immunohistochemistry in combination with antibody-based cellular phenotyping following electrical stimulation of the mesencephalic locomotor region (MLR) – the anatomical constituents of which remain debated today, primarily between the cuneiform (CnF) and the pedunculopontine tegmental nuclei (PPT). Effective MLR sites were co-extensive with the CnF nucleus. Animals subject to the locomotor task showed abundant Fos labeling in the CnF, parabrachial nuclei of the subcuneiform region, periaqueductal gray, locus ceruleus (LC)/subceruleus (SubC), Kölliker–Fuse, magnocellular and lateral tegmental fields, raphe, and the parapyramidal region. Labeled neurons were more abundant on the side of stimulation. In some animals, Fos-labeled cells were also observed in the ventral tegmental area, medial and intermediate vestibular nuclei, dorsal motor nucleus of the vagus, n. tractus solitarii, and retrofacial nucleus in the ventrolateral medulla. Many neurons in the reticular formation were innervated by serotonergic fibers. Numerous locomotor-activated neurons in the parabrachial nuclei and LC/SubC/Kölliker–Fuse were noradrenergic. Few cholinergic neurons within the PPT stained for Fos. In the medulla, serotonergic neurons within the parapyramidal region and the nucleus raphe magnus were positive for Fos. Control animals, not subject to locomotion, showed few Fos-labeled neurons in these areas. The current study provides positive evidence for a role for the CnF in the initiation of locomotion while providing little evidence for the participation of the PPT. The results also show that MLR-evoked locomotion involves the parallel activation of reticular and monoaminergic neurons in the pons/medulla, and provides the anatomical and functional basis for spinal monoamine release during evoked locomotion. Lastly, the results indicate that vestibular, cardiovascular, and respiratory centers are centrally activated during MLR-evoked locomotion. Altogether, the results show a complex pattern of neuromodulatory influences of brainstem neurons by electrical activation of the MLR.
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Affiliation(s)
- Ioan Opris
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Xiaohong Dai
- Department of Physiology, Spinal Cord Research Centre, University of Manitoba, Winnipeg, MB, Canada
| | - Dawn M G Johnson
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Francisco J Sanchez
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Luz M Villamil
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Songtao Xie
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Cecelia R Lee-Hauser
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Stephano Chang
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Larry M Jordan
- Department of Physiology, Spinal Cord Research Centre, University of Manitoba, Winnipeg, MB, Canada
| | - Brian R Noga
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
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Tamura K, Sugita S, Tokunaga T, Minegishi Y, Ota N. TRPM8-mediated cutaneous stimulation modulates motor neuron activity during treadmill stepping in mice. J Physiol Sci 2019; 69:931-938. [PMID: 31482469 PMCID: PMC10717255 DOI: 10.1007/s12576-019-00707-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 08/26/2019] [Indexed: 11/29/2022]
Abstract
Motor units are generally recruited from the smallest to the largest following the size principle, while cutaneous stimulation has the potential to affect spinal motor control. We aimed to examine the effects of stimulating transient receptor potential channel sub-family M8 (TRPM8) combined with exercise on the modulation of spinal motor neuron (MN) excitability. Mice were topically administrated 1.5% icilin on the hindlimbs, followed by treadmill stepping. Spinal cord sections were immunostained with antibodies against c-fos and choline acetyltransferase. Icilin stimulation did not change the number of c-fos+ MNs, but increased the average soma size of the c-fos+ MNs during low-speed treadmill stepping. Furthermore, icilin stimulation combined with stepping increased c-fos+ cholinergic interneurons near the central canal, which are thought to modulate MN excitability. These findings suggest that TRPM8-mediated cutaneous stimulation with low-load exercise promotes preferential recruitment of large MNs and is potentially useful as a new training method for rehabilitation.
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Affiliation(s)
- Kotaro Tamura
- Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi, 321-3497, Japan
| | - Satoshi Sugita
- Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi, 321-3497, Japan
| | - Tadayuki Tokunaga
- Personal Health Care Products Research, Kao Corporation, Tokyo, Japan
| | - Yoshihiko Minegishi
- Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi, 321-3497, Japan.
| | - Noriyasu Ota
- Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi, 321-3497, Japan
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14
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Balanced cholinergic modulation of spinal locomotor circuits via M2 and M3 muscarinic receptors. Sci Rep 2019; 9:14051. [PMID: 31575899 PMCID: PMC6773880 DOI: 10.1038/s41598-019-50452-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 09/12/2019] [Indexed: 01/05/2023] Open
Abstract
Neuromodulation ensures that neural circuits produce output that is flexible whilst remaining within an optimal operational range. The neuromodulator acetylcholine is released during locomotion to regulate spinal motor circuits. However, the range of receptors and downstream mechanisms by which acetylcholine acts have yet to be fully elucidated. We therefore investigated metabotropic acetylcholine receptor-mediated modulation by using isolated spinal cord preparations from neonatal mice in which locomotor-related output can be induced pharmacologically. We report that M2 receptor blockade decreases the frequency and amplitude of locomotor-related activity, whilst reducing its variability. In contrast, M3 receptor blockade destabilizes locomotor-related bursting. Motoneuron recordings from spinal cord slices revealed that activation of M2 receptors induces an outward current, decreases rheobase, reduces the medium afterhyperpolarization, shortens spike duration and decreases synaptic inputs. In contrast, M3 receptor activation elicits an inward current, increases rheobase, extends action potential duration and increases synaptic inputs. Analysis of miniature postsynaptic currents support that M2 and M3 receptors modulate synaptic transmission via different mechanisms. In summary, we demonstrate that M2 and M3 receptors have opposing modulatory actions on locomotor circuit output, likely reflecting contrasting cellular mechanisms of action. Thus, intraspinal cholinergic systems mediate balanced, multimodal control of spinal motor output.
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15
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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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16
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Merkulyeva N, Lyakhovetskii V, Veshchitskii A, Bazhenova E, Gorskii O, Musienko P. Activation of the spinal neuronal network responsible for visceral control during locomotion. Exp Neurol 2019; 320:112986. [PMID: 31254518 DOI: 10.1016/j.expneurol.2019.112986] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 05/19/2019] [Accepted: 06/25/2019] [Indexed: 12/21/2022]
Abstract
It has been established that stepping of the decerebrate cat was accompanied by involvement of the urinary system: external urethral sphincter (EUS) and detrusor muscle activation, as well as the corresponding increase of the intravesical pressure. Detrusor and EUS evoked EMG activity matched the limbs locomotor movements. Immunohistochemical labeling of the immediate early gene c-fos expression was used to reveal the neural mechanisms of such somatovisceral interconnection within the sacral neural pathways. Study showed that two locomotor modes (forward and backward walking) had significantly different kinematic features. Combining the different immunohistochemical methods, we found that many c-fos-immunopositive nuclei were localized within several visceral areas of the S2 spinal segment which matched the sacral parasympathetic nucleus and dorsal gray commissure. Cats stepping backward had 4-fold more c-fos-immunopositive nuclei within the ventrolateral part of the sacral parasympathetic nucleus apparently correspondent to the "lateral band" contained cells controlling bladder function. The present work provides the direct evidences of visceral neurons activation depending on the specific of locomotor pattern and confirms the somatovisceral integration carrying out on the spinal cord level.
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Affiliation(s)
- Natalia Merkulyeva
- Pavlov Institute of Physiology RAS, Saint-Petersburg, Makarov emb., 6, 199034, Russia; Russian Research Center of Radiology and Surgical Technologies, Ministry of Health of the RF, Saint-Petersburg, poselok Pesochnyy, Leningradskaya str., 70, 197758, Russia; Institute of Translational Biomedicine, Saint-Petersburg State University, Saint-Petersburg, Universitetskaya emb., 7-9, 199034, Russia
| | - Vsevolod Lyakhovetskii
- Pavlov Institute of Physiology RAS, Saint-Petersburg, Makarov emb., 6, 199034, Russia; Russian Research Center of Radiology and Surgical Technologies, Ministry of Health of the RF, Saint-Petersburg, poselok Pesochnyy, Leningradskaya str., 70, 197758, Russia
| | | | - Elena Bazhenova
- Pavlov Institute of Physiology RAS, Saint-Petersburg, Makarov emb., 6, 199034, Russia; Institute of Translational Biomedicine, Saint-Petersburg State University, Saint-Petersburg, Universitetskaya emb., 7-9, 199034, Russia
| | - Oleg Gorskii
- Pavlov Institute of Physiology RAS, Saint-Petersburg, Makarov emb., 6, 199034, Russia; Russian Research Center of Radiology and Surgical Technologies, Ministry of Health of the RF, Saint-Petersburg, poselok Pesochnyy, Leningradskaya str., 70, 197758, Russia; Institute of Translational Biomedicine, Saint-Petersburg State University, Saint-Petersburg, Universitetskaya emb., 7-9, 199034, Russia
| | - Pavel Musienko
- Pavlov Institute of Physiology RAS, Saint-Petersburg, Makarov emb., 6, 199034, Russia; Russian Research Center of Radiology and Surgical Technologies, Ministry of Health of the RF, Saint-Petersburg, poselok Pesochnyy, Leningradskaya str., 70, 197758, Russia; Institute of Translational Biomedicine, Saint-Petersburg State University, Saint-Petersburg, Universitetskaya emb., 7-9, 199034, Russia; Children's Surgery and Orthopedic Clinic, Department of Non-pulmonary Tuberculosis, Research Institute of Phthysiopulmonology, Saint-Petersburg, Politekhnicheskaya str., 32, 194064, Russia.
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17
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Intramuscular Injection of Adenoassociated Virus Encoding Human Neurotrophic Factor 3 and Exercise Intervention Contribute to Reduce Spasms after Spinal Cord Injury. Neural Plast 2019; 2019:3017678. [PMID: 30984254 PMCID: PMC6432737 DOI: 10.1155/2019/3017678] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 10/12/2018] [Accepted: 10/23/2018] [Indexed: 01/08/2023] Open
Abstract
Limb spasms are phenomena of hyperreflexia that occur after spinal cord injury. Currently, the clinical treatment is less than ideal. Our goal is to develop a combination therapy based on individualized medicine to reduce spasticity after spinal cord injury. In this study, rats received a severe contusive injury at the T9 segment of the spinal cord, followed by gene therapy with adenoassociated virus encoding human neurotrophic factor 3 (AAV-NT3) and a 2-week exercise program starting at 4 weeks after injury. We quantified the frequency of spasms during a swimming test at 4 and 6 weeks after injury and confirmed the results of the swimming test by measuring the H-reflex of the plantar muscle. We obtained weekly hind limb exercise scores to assess the effect of the interventions in hind limb motor function improvement. Then, we used immunofluorescence to observe the immunoreactivity of spinal motor neurons, synaptophysin, cholinergic interneurons, and GABAergic interneurons. We also measured the expression of KCC2 in the spinal cord by western blot. We found that AAV-NT3 gene therapy, exercise, and combination therapy all attenuated the frequency of spasms in the swimming test conducted at 6 weeks after spinal cord injury and increased rate-dependent depression of H-reflex. Combination therapy was significantly superior to AAV-NT3 alone in protecting motor neurons. Recovery of KCC2 expression was significantly greater in rats treated with combination therapy than in the exercise group. Combination therapy was also significantly superior to individual therapies in remodeling spinal cord neurons. Our study shows that the combination of AAV-NT3 gene therapy and exercise can alleviate muscle spasm after spinal cord injury by altering the excitability of spinal interneurons and motor neurons. However, combination therapy did not show a significant additive effect, which needs to be improved by adjusting the combined strategy.
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18
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Thornton MA, Mehta MD, Morad TT, Ingraham KL, Khankan RR, Griffis KG, Yeung AK, Zhong H, Roy RR, Edgerton VR, Phelps PE. Evidence of axon connectivity across a spinal cord transection in rats treated with epidural stimulation and motor training combined with olfactory ensheathing cell transplantation. Exp Neurol 2018; 309:119-133. [PMID: 30056160 PMCID: PMC6365019 DOI: 10.1016/j.expneurol.2018.07.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 07/18/2018] [Accepted: 07/24/2018] [Indexed: 12/16/2022]
Abstract
Olfactory ensheathing cells (OECs) are unique glia that support axon outgrowth in the olfactory system, and when used as cellular therapy after spinal cord injury, improve recovery and axon regeneration. Here we assessed the effects of combining OEC transplantation with another promising therapy, epidural electrical stimulation during a rehabilitative motor task. Sprague-Dawley rats received a mid-thoracic transection and transplantation of OECs or fibroblasts (FBs) followed by lumbar stimulation while climbing an inclined grid. We injected pseudorabies virus (PRV) into hindlimb muscles 7 months post-injury to assess connectivity across the transection. Analyses showed that the number of serotonergic (5-HT) axons that crossed the rostral scar border and the area of neurofilament-positive axons in the injury site were both greater in OEC- than FB-treated rats. We detected PRV-labeled cells rostral to the transection and remarkable evidence of 5-HT and PRV axons crossing the injury site in 1 OEC- and 1 FB-treated rat. The axons that crossed suggested either axon regeneration (OEC) or small areas of probable tissue sparing (FB). Most PRV-labeled thoracic neurons were detected in laminae VII or X, and ~25% expressed Chx10, a marker for V2a interneurons. These findings suggest potential regeneration or sparing of circuits that connect thoracic interneurons to lumbar somatic motor neurons. Despite evidence of axonal connectivity, no behavioral changes were detected in this small-scale study. Together these data suggest that when supplemented with epidural stimulation and climbing, OEC transplantation can increase axonal growth across the injury site and may promote recovery of propriospinal circuitry.
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Affiliation(s)
- Michael A Thornton
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States
| | - Manan D Mehta
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States
| | - Tyler T Morad
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States
| | - Kaitlin L Ingraham
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States; Molecular, Cellular and Integrative Physiology, Interdepartmental Ph.D. Program, UCLA, Los Angeles, CA 90095, United States
| | - Rana R Khankan
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States; Molecular, Cellular and Integrative Physiology, Interdepartmental Ph.D. Program, UCLA, Los Angeles, CA 90095, United States
| | - Khris G Griffis
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States; Molecular, Cellular and Integrative Physiology, Interdepartmental Ph.D. Program, UCLA, Los Angeles, CA 90095, United States
| | - Anthony K Yeung
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States
| | - Hui Zhong
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States
| | - Roland R Roy
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States; Brain Research Institute, UCLA, Los Angeles, CA 90095, United States
| | - V Reggie Edgerton
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States; Molecular, Cellular and Integrative Physiology, Interdepartmental Ph.D. Program, UCLA, Los Angeles, CA 90095, United States; Brain Research Institute, UCLA, Los Angeles, CA 90095, United States
| | - Patricia E Phelps
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095, United States; Molecular, Cellular and Integrative Physiology, Interdepartmental Ph.D. Program, UCLA, Los Angeles, CA 90095, United States; Brain Research Institute, UCLA, Los Angeles, CA 90095, United States.
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Więckowska A, Gajewska-Woźniak O, Głowacka A, Ji B, Grycz K, Czarkowska-Bauch J, Skup M. Spinalization and locomotor training differentially affect muscarinic acetylcholine receptor type 2 abutting on α-motoneurons innervating the ankle extensor and flexor muscles. J Neurochem 2018; 147:361-379. [DOI: 10.1111/jnc.14567] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 07/10/2018] [Accepted: 08/06/2018] [Indexed: 11/27/2022]
Affiliation(s)
| | | | - Anna Głowacka
- Nencki Institute of Experimental Biology; Warsaw Poland
| | - Benjun Ji
- Nencki Institute of Experimental Biology; Warsaw Poland
| | - Kamil Grycz
- Nencki Institute of Experimental Biology; Warsaw Poland
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20
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Transneuronal Downregulation of the Premotor Cholinergic System After Corticospinal Tract Loss. J Neurosci 2018; 38:8329-8344. [PMID: 30049887 DOI: 10.1523/jneurosci.3410-17.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Revised: 07/13/2018] [Accepted: 07/18/2018] [Indexed: 12/31/2022] Open
Abstract
Injury to the supraspinal motor systems, especially the corticospinal tract, leads to movement impairments. In addition to direct disruption of descending motor pathways, spinal motor circuits that are distant to and not directly damaged by the lesion undergo remodeling that contributes significantly to the impairments. Knowing which spinal circuits are remodeled and the underlying mechanisms are critical for understanding the functional changes in the motor pathway and for developing repair strategies. Here, we target spinal premotor cholinergic interneurons (IN) that directly modulate motoneuron excitability via their cholinergic C-bouton terminals. Using a model of unilateral medullary corticospinal tract lesion in male rats, we found transneuronal downregulation of the premotor cholinergic pathway. Phagocytic microglial cells were upregulated in parallel with cholinergic pathway downregulation and both were blocked by minocycline, a microglia activation inhibitor. Additionally, we found a transient increase in interneuronal complement protein C1q expression that preceded cell loss. 3D reconstructions showed ongoing phagocytosis of C1q-expressing cholinergic INs by microglia 3 d after injury, which was complete by 10 d after injury. Unilateral motor cortex inactivation using the GABAA receptor agonist muscimol replicated the changes detected at 3 d after lesion, indicating activity dependence. The neuronal loss after the lesion was rescued by increasing spinal activity using cathodal trans-spinal direct current stimulation. Our finding of activity-dependent modulation of cholinergic premotor INs after CST injury provides the mechanistic insight that maintaining activity, possibly during a critical period, helps to protect distant motor circuits from further damage and, as a result, may improve motor functional recovery and rehabilitation.SIGNIFICANCE STATEMENT Supraspinal injury to the motor system disrupts descending motor pathways, leading to movement impairments. Whether and how intrinsic spinal circuits are remodeled after a brain injury is unclear. Using a rat model of unilateral corticospinal tract lesion in the medulla, we show activity-dependent, transneuronal downregulation of the spinal premotor cholinergic system, which is mediated by microglial phagocytosis, possibly involving a rapid and transient increase in neuronal C1q before neuronal loss. Spinal cord neuromodulation after injury to augment spinal activity rescued the premotor cholinergic system. Our findings provide the mechanistic insight that maintaining activity, possibly during an early critical period, could protect distant motor circuits from further damage mediated by microglia and interneuronal complement protein and improve motor functional outcomes.
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21
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Sourioux M, Bertrand SS, Cazalets JR. Cholinergic-mediated coordination of rhythmic sympathetic and motor activities in the newborn rat spinal cord. PLoS Biol 2018; 16:e2005460. [PMID: 29985914 PMCID: PMC6053244 DOI: 10.1371/journal.pbio.2005460] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 07/19/2018] [Accepted: 06/22/2018] [Indexed: 02/07/2023] Open
Abstract
Here, we investigated intrinsic spinal cord mechanisms underlying the physiological requirement for autonomic and somatic motor system coupling. Using an in vitro spinal cord preparation from newborn rat, we demonstrate that the specific activation of muscarinic cholinergic receptors (mAchRs) (with oxotremorine) triggers a slow burst rhythm in thoracic spinal segments, thereby revealing a rhythmogenic capability in this cord region. Whereas axial motoneurons (MNs) were rhythmically activated during both locomotor activity and oxotremorine-induced bursting, intermediolateral sympathetic preganglionic neurons (IML SPNs) exhibited rhythmicity solely in the presence of oxotremorine. This somato-sympathetic synaptic drive shared by MNs and IML SPNs could both merge with and modulate the locomotor synaptic drive produced by the lumbar motor networks. This study thus sheds new light on the coupling between somatic and sympathetic systems and suggests that an intraspinal network that may be conditionally activated under propriospinal cholinergic control constitutes at least part of the synchronizing mechanism.
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Affiliation(s)
| | | | - Jean-René Cazalets
- Université de Bordeaux, CNRS UMR 5287, Bordeaux, France
- * E-mail: (JRC); (SSB)
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Porter NJ, Li WC. Muscarinic modulation of the Xenopus laevis tadpole spinal mechanosensory pathway. Brain Res Bull 2018; 139:278-284. [DOI: 10.1016/j.brainresbull.2018.03.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 03/19/2018] [Accepted: 03/24/2018] [Indexed: 02/06/2023]
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23
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Sathyamurthy A, Johnson KR, Matson KJE, Dobrott CI, Li L, Ryba AR, Bergman TB, Kelly MC, Kelley MW, Levine AJ. Massively Parallel Single Nucleus Transcriptional Profiling Defines Spinal Cord Neurons and Their Activity during Behavior. Cell Rep 2018; 22:2216-2225. [PMID: 29466745 PMCID: PMC5849084 DOI: 10.1016/j.celrep.2018.02.003] [Citation(s) in RCA: 221] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 12/19/2017] [Accepted: 01/30/2018] [Indexed: 01/08/2023] Open
Abstract
To understand the cellular basis of behavior, it is necessary to know the cell types that exist in the nervous system and their contributions to function. Spinal networks are essential for sensory processing and motor behavior and provide a powerful system for identifying the cellular correlates of behavior. Here, we used massively parallel single nucleus RNA sequencing (snRNA-seq) to create an atlas of the adult mouse lumbar spinal cord. We identified and molecularly characterized 43 neuronal populations. Next, we leveraged the snRNA-seq approach to provide unbiased identification of neuronal populations that were active following a sensory and a motor behavior, using a transcriptional signature of neuronal activity. This approach can be used in the future to link single nucleus gene expression data with dynamic biological responses to behavior, injury, and disease.
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Affiliation(s)
- Anupama Sathyamurthy
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Kory R Johnson
- Bioinformatics Section, Information Technology Program, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Kaya J E Matson
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Courtney I Dobrott
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Li Li
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Anna R Ryba
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Tzipporah B Bergman
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Michael C Kelly
- Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, Bethesda, MD 20892, USA
| | - Matthew W Kelley
- Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, Bethesda, MD 20892, USA
| | - Ariel J Levine
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA.
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Taccola G, Sayenko D, Gad P, Gerasimenko Y, Edgerton VR. And yet it moves: Recovery of volitional control after spinal cord injury. Prog Neurobiol 2017; 160:64-81. [PMID: 29102670 PMCID: PMC5773077 DOI: 10.1016/j.pneurobio.2017.10.004] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 10/09/2017] [Accepted: 10/21/2017] [Indexed: 12/12/2022]
Abstract
Preclinical and clinical neurophysiological and neurorehabilitation research has generated rather surprising levels of recovery of volitional sensory-motor function in persons with chronic motor paralysis following a spinal cord injury. The key factor in this recovery is largely activity-dependent plasticity of spinal and supraspinal networks. This key factor can be triggered by neuromodulation of these networks with electrical and pharmacological interventions. This review addresses some of the systems-level physiological mechanisms that might explain the effects of electrical modulation and how repetitive training facilitates the recovery of volitional motor control. In particular, we substantiate the hypotheses that: (1) in the majority of spinal lesions, a critical number and type of neurons in the region of the injury survive, but cannot conduct action potentials, and thus are electrically non-responsive; (2) these neuronal networks within the lesioned area can be neuromodulated to a transformed state of electrical competency; (3) these two factors enable the potential for extensive activity-dependent reorganization of neuronal networks in the spinal cord and brain, and (4) propriospinal networks play a critical role in driving this activity-dependent reorganization after injury. Real-time proprioceptive input to spinal networks provides the template for reorganization of spinal networks that play a leading role in the level of coordination of motor pools required to perform a given functional task. Repetitive exposure of multi-segmental sensory-motor networks to the dynamics of task-specific sensory input as occurs with repetitive training can functionally reshape spinal and supraspinal connectivity thus re-enabling one to perform complex motor tasks, even years post injury.
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Affiliation(s)
- G Taccola
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095 USA; Neuroscience Department, International School for Advanced Studies (SISSA), Bonomea 265, Trieste, Italy
| | - D Sayenko
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095 USA
| | - P Gad
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095 USA
| | - Y Gerasimenko
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095 USA; Pavlov Institute of Physiology, St. Petersburg 199034, Russia
| | - V R Edgerton
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095 USA; Department of Neurobiology, University of California, Los Angeles, CA 90095 USA; Department of Neurosurgery, University of California, Los Angeles, CA 90095 USA; Brain Research Institute, University of California, Los Angeles, CA 90095 USA; The Centre for Neuroscience and Regenerative Medicine, Faculty of Science, University of Technology Sydney, Ultimo, 2007 NSW, Australia; Institut Guttmann, Hospital de Neurorehabilitació, Institut Universitari adscrit a la Universitat Autònoma de Barcelona, Barcelona, 08916 Badalona, Spain.
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25
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Noga BR, Turkson RP, Xie S, Taberner A, Pinzon A, Hentall ID. Monoamine Release in the Cat Lumbar Spinal Cord during Fictive Locomotion Evoked by the Mesencephalic Locomotor Region. Front Neural Circuits 2017; 11:59. [PMID: 28912689 PMCID: PMC5582069 DOI: 10.3389/fncir.2017.00059] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 08/09/2017] [Indexed: 01/28/2023] Open
Abstract
Spinal cord neurons active during locomotion are innervated by descending axons that release the monoamines serotonin (5-HT) and norepinephrine (NE) and these neurons express monoaminergic receptor subtypes implicated in the control of locomotion. The timing, level and spinal locations of release of these two substances during centrally-generated locomotor activity should therefore be critical to this control. These variables were measured in real time by fast-cyclic voltammetry in the decerebrate cat's lumbar spinal cord during fictive locomotion, which was evoked by electrical stimulation of the mesencephalic locomotor region (MLR) and registered as integrated activity in bilateral peripheral nerves to hindlimb muscles. Monoamine release was observed in dorsal horn (DH), intermediate zone/ventral horn (IZ/VH) and adjacent white matter (WM) during evoked locomotion. Extracellular peak levels (all sites) increased above baseline by 138 ± 232.5 nM and 35.6 ± 94.4 nM (mean ± SD) for NE and 5-HT, respectively. For both substances, release usually began prior to the onset of locomotion typically earliest in the IZ/VH and peaks were positively correlated with net activity in peripheral nerves. Monoamine levels gradually returned to baseline levels or below at the end of stimulation in most trials. Monoamine oxidase and uptake inhibitors increased the release magnitude, time-to-peak (TTP) and decline-to-baseline. These results demonstrate that spinal monoamine release is modulated on a timescale of seconds, in tandem with centrally-generated locomotion and indicate that MLR-evoked locomotor activity involves concurrent activation of descending monoaminergic and reticulospinal pathways. These gradual changes in space and time of monoamine concentrations high enough to strongly activate various receptors subtypes on locomotor activated neurons further suggest that during MLR-evoked locomotion, monoamine action is, in part, mediated by extrasynaptic neurotransmission in the spinal cord.
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Affiliation(s)
- Brian R Noga
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of MedicineMiami, FL, United States
| | - Riza P Turkson
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of MedicineMiami, FL, United States
| | - Songtao Xie
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of MedicineMiami, FL, United States
| | - Annette Taberner
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of MedicineMiami, FL, United States
| | - Alberto Pinzon
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of MedicineMiami, FL, United States
| | - Ian D Hentall
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of MedicineMiami, FL, United States
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26
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Côté MP, Murray M, Lemay MA. Rehabilitation Strategies after Spinal Cord Injury: Inquiry into the Mechanisms of Success and Failure. J Neurotrauma 2016; 34:1841-1857. [PMID: 27762657 DOI: 10.1089/neu.2016.4577] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Body-weight supported locomotor training (BWST) promotes recovery of load-bearing stepping in lower mammals, but its efficacy in individuals with a spinal cord injury (SCI) is limited and highly dependent on injury severity. While animal models with complete spinal transections recover stepping with step-training, motor complete SCI individuals do not, despite similarly intensive training. In this review, we examine the significant differences between humans and animal models that may explain this discrepancy in the results obtained with BWST. We also summarize the known effects of SCI and locomotor training on the muscular, motoneuronal, interneuronal, and supraspinal systems in human and non-human models of SCI and address the potential causes for failure to translate to the clinic. The evidence points to a deficiency in neuronal activation as the mechanism of failure, rather than muscular insufficiency. While motoneuronal and interneuronal systems cannot be directly probed in humans, the changes brought upon by step-training in SCI animal models suggest a beneficial re-organization of the systems' responsiveness to descending and afferent feedback that support locomotor recovery. The literature on partial lesions in humans and animal models clearly demonstrate a greater dependency on supraspinal input to the lumbar cord in humans than in non-human mammals for locomotion. Recent results with epidural stimulation that activates the lumbar interneuronal networks and/or increases the overall excitability of the locomotor centers suggest that these centers are much more dependent on the supraspinal tonic drive in humans. Sensory feedback shapes the locomotor output in animal models but does not appear to be sufficient to drive it in humans.
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Affiliation(s)
- Marie-Pascale Côté
- 1 Department of Neurobiology and Anatomy, Drexel University College of Medicine , Philadelphia, Pennsylvania
| | - Marion Murray
- 1 Department of Neurobiology and Anatomy, Drexel University College of Medicine , Philadelphia, Pennsylvania
| | - Michel A Lemay
- 2 Department of Bioengineering, Temple University , Philadelphia, Pennsylvania
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27
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Lombardo J, Harrington MA. Nonreciprocal mechanisms in up- and downregulation of spinal motoneuron excitability by modulators of KCNQ/Kv7 channels. J Neurophysiol 2016; 116:2114-2124. [PMID: 27512022 DOI: 10.1152/jn.00446.2016] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/05/2016] [Indexed: 12/11/2022] Open
Abstract
KCNQ/Kv7 channels form a slow noninactivating K+ current, also known as the M current. They activate in the subthreshold range of membrane potentials and regulate different aspects of excitability in neurons of the central nervous system. In spinal motoneurons (MNs), KCNQ/Kv7 channels have been identified in the somata, axonal initial segment, and nodes of Ranvier, where they generate a slow, noninactivating, K+ current sensitive to both muscarinic receptor-mediated inhibition and KCNQ/Kv7 channel blockers. In this study, we thoroughly reevaluated the function of up- and downregulation of KCNQ/Kv7 channels in mouse immature spinal MNs. Using electrophysiological techniques together with specific pharmacological modulators of the activity of KCNQ/Kv7 channels, we show that enhancement of the activity of these channels decreases the excitability of spinal MNs in mouse neonates. This action on MNs results from a combination of hyperpolarization of the resting membrane potential, a decrease in the input resistance, and depolarization of the voltage threshold. On the other hand, the effect of inhibition of KCNQ/Kv7 channels suggested that these channels play a limited role in regulating basal excitability. Computer simulations confirmed that pharmacological enhancement of KCNQ/Kv7 channel activity decreases excitability and also suggested that the effects of inhibition of KCNQ/Kv7 channels on the excitability of spinal MNs do not depend on a direct effect in these neurons but likely on spinal cord synaptic partners. These results indicate that KCNQ/Kv7 channels have a fundamental role in the modulation of the excitability of spinal MNs acting both in these neurons and in their local presynaptic partners.
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Affiliation(s)
- Joseph Lombardo
- Department of Biological Sciences, Delaware State University, Dover, Delaware
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28
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Alford S, Schwartz E, Viana di Prisco G. The Pharmacology of Vertebrate Spinal Central Pattern Generators. Neuroscientist 2016; 9:217-28. [PMID: 15065817 DOI: 10.1177/1073858403009003014] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Central pattern generators are networks of neurons capable of generating an output pattern of spike activity in a relatively stereotyped, rhythmic pattern that has been found to underlie vital functions like respiration and locomotion. The central pattern generator for locomotion in vertebrates seems to share some basic building blocks. Activation and excitation of activity is driven by descending, sensory, and intraspinal glutamatergic neurons. NMDA receptor activation may also lead to the activation of oscillatory properties in individual neurons that depend on an array of ion channels situated in those neurons. Coordination across joints or the midline of the animal is driven primarily by glycinergic inhibition. In addition to these processes, numerous modulatory mechanisms alter the function of the central pattern generator. These include metabotropic amino acid receptors activated by rhythmic release of glutamate and GABA as well as monoamines, ACh, and peptides. Function and stability of the central pattern generator is also critically dependent on the array of ion channels found in neurons that compose these oscillators, including Ca2+and voltage-gated K+channels and Ca2+channels.
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Affiliation(s)
- Simon Alford
- Department of Biological Sciences, University of Illinois at Chicago, 60607, USA.
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29
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Duru PO, Tillakaratne NJK, Kim JA, Zhong H, Stauber SM, Pham TT, Xiao MS, Edgerton VR, Roy RR. Spinal neuronal activation during locomotor-like activity enabled by epidural stimulation and 5-hydroxytryptamine agonists in spinal rats. J Neurosci Res 2015; 93:1229-39. [PMID: 25789848 DOI: 10.1002/jnr.23579] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/05/2015] [Accepted: 02/08/2015] [Indexed: 12/28/2022]
Abstract
UNLABELLED The neural networks that generate stepping in complete spinal adult rats remain poorly defined. To address this problem, we used c-fos (an activity-dependent marker) to identify active interneurons and motoneurons in the lumbar spinal cord of adult spinal rats during a 30-min bout of bipedal stepping. Spinal rats were either step trained (30 min/day, 3 days/week, for 7.5 weeks) or not step trained. Stepping was enabled by epidural stimulation and the administration of the serotonergic agonists quipazine and 8-OHDPAT. A third group of spinal rats served as untreated (no stimulation, drugs, or stepping) controls. The numbers of activated cholinergic central canal cluster cells and partition neurons were higher in both step-trained and nontrained rats than in untreated rats and were higher in nontrained than in step-trained rats. The latter finding suggests that daily treatment with epidural stimulation plus serotonergic agonist treatment without step training enhances the excitability of a broader cholinergic interneuronal population than does step training. The numbers of activated interneurons in laminae II-VI of lumbar cross-sections were higher in both step-trained and nontrained rats than in untreated rats, and they were highest in step-trained rats. This finding suggests that this population of interneurons is responsive to epidural stimulation plus serotonergic treatment and that load-bearing induced when stepping has an additive effect. The numbers of activated motoneurons of all size categories were higher in the step-trained group than in the other two groups, reflecting a strong effect of loading on motoneuron recruitment. In general, these results indicate that the spinal networks for locomotion are similar with and without brain input. SIGNIFICANCE We identified neurons within the spinal cord networks that are activated during assisted stepping in paraplegic rats. We stimulated the spinal cord and administered a drug to help the rats step. One group was trained to step and another was not trained. We observed a lower percentage of activated neurons in specific spinal cord regions in trained rats than in nontrained rats after a 1-hr stepping bout, suggesting that step training reduces activation of some types of spinal neurons. This observation indicates that training makes the spinal networks more efficient and suggests a "learning" phenomenon in the spinal cord without any brain input.
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Affiliation(s)
- Paul O Duru
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California
| | - Niranjala J K Tillakaratne
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California.,Brain Research Institute, University of California, Los Angeles, Los Angeles, California
| | - Jung A Kim
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California
| | - Hui Zhong
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California
| | - Stacey M Stauber
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California
| | - Trinh T Pham
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California
| | - Mei S Xiao
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California
| | - V Reggie Edgerton
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California.,Brain Research Institute, University of California, Los Angeles, Los Angeles, California.,Department of Neurosurgery, University of California, Los Angeles, Los Angeles, California.,Department of Neurobiology, University of California, Los Angeles, Los Angeles, California
| | - Roland R Roy
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California.,Brain Research Institute, University of California, Los Angeles, Los Angeles, California
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30
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Jordan LM, McVagh JR, Noga BR, Cabaj AM, Majczyński H, Sławińska U, Provencher J, Leblond H, Rossignol S. Cholinergic mechanisms in spinal locomotion-potential target for rehabilitation approaches. Front Neural Circuits 2014; 8:132. [PMID: 25414645 PMCID: PMC4222238 DOI: 10.3389/fncir.2014.00132] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 10/13/2014] [Indexed: 01/08/2023] Open
Abstract
Previous experiments implicate cholinergic brainstem and spinal systems in the control of locomotion. Our results demonstrate that the endogenous cholinergic propriospinal system, acting via M2 and M3 muscarinic receptors, is capable of consistently producing well-coordinated locomotor activity in the in vitro neonatal preparation, placing it in a position to contribute to normal locomotion and to provide a basis for recovery of locomotor capability in the absence of descending pathways. Tests of these suggestions, however, reveal that the spinal cholinergic system plays little if any role in the induction of locomotion, because MLR-evoked locomotion in decerebrate cats is not prevented by cholinergic antagonists. Furthermore, it is not required for the development of stepping movements after spinal cord injury, because cholinergic agonists do not facilitate the appearance of locomotion after spinal cord injury, unlike the dramatic locomotion-promoting effects of clonidine, a noradrenergic α-2 agonist. Furthermore, cholinergic antagonists actually improve locomotor activity after spinal cord injury, suggesting that plastic changes in the spinal cholinergic system interfere with locomotion rather than facilitating it. Changes that have been observed in the cholinergic innervation of motoneurons after spinal cord injury do not decrease motoneuron excitability, as expected. Instead, the development of a “hyper-cholinergic” state after spinal cord injury appears to enhance motoneuron output and suppress locomotion. A cholinergic suppression of afferent input from the limb after spinal cord injury is also evident from our data, and this may contribute to the ability of cholinergic antagonists to improve locomotion. Not only is a role for the spinal cholinergic system in suppressing locomotion after SCI suggested by our results, but an obligatory contribution of a brainstem cholinergic relay to reticulospinal locomotor command systems is not confirmed by our experiments.
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Affiliation(s)
- Larry M Jordan
- Department of Physiology and Pathophysiology, Spinal Cord Research Centre, University of Manitoba Winnipeg, MB, Canada
| | - J R McVagh
- Department of Physiology and Pathophysiology, Spinal Cord Research Centre, University of Manitoba Winnipeg, MB, Canada
| | - B R Noga
- Department of Neurological Surgery, The Miami Project to Cure Paralysis, University of Miami Miami, FL, USA
| | - A M Cabaj
- Department of Neurophysiology, Nencki Institute of Experimental Biology PAS Warsaw, Poland ; Department of Nerve-Muscle Engineering, Institute of Biocybernetics and Biomedical Engineering PAS Warsaw, Poland
| | - H Majczyński
- Department of Neurophysiology, Nencki Institute of Experimental Biology PAS Warsaw, Poland
| | - Urszula Sławińska
- Department of Neurophysiology, Nencki Institute of Experimental Biology PAS Warsaw, Poland
| | - J Provencher
- Groupe de Recherche sur le Système Nerveux Central and Department of Neuroscience, Faculty of Medicine, Université de Montréal Montreal, QC, Canada
| | - H Leblond
- Groupe de Recherche sur le Système Nerveux Central and Department of Neuroscience, Faculty of Medicine, Université de Montréal Montreal, QC, Canada
| | - Serge Rossignol
- Groupe de Recherche sur le Système Nerveux Central and Department of Neuroscience, Faculty of Medicine, Université de Montréal Montreal, QC, Canada
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31
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Tillakaratne NJK, Duru P, Fujino H, Zhong H, Xiao MS, Edgerton VR, Roy RR. Identification of interneurons activated at different inclines during treadmill locomotion in adult rats. J Neurosci Res 2014; 92:1714-22. [PMID: 24975393 DOI: 10.1002/jnr.23437] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 05/19/2014] [Accepted: 05/22/2014] [Indexed: 12/17/2022]
Abstract
By using c-fos as an activity-dependent marker, we identified the cholinergic interneurons around the central canal and lumbar interneurons throughout the gray matter that were activated after a 30-min bout of quadrupedal treadmill stepping at a 0° or 25° incline in adult rats. Increased loading (elevated treadmill incline) imposed during treadmill stepping activated more cholinergic interneurons in the proximity of the central canal, i.e., central canal cluster cells and partition neurons. Since cholinergic central canal cells are thought to modulate motoneuron excitability, these data suggest that increased load during stepping may increase motoneuronal activity through activating more cholinergic central canal cells. We identified the muscle-specific motoneurons and afferent terminals in the spinal cord by injecting cholera toxin subunit B in the soleus and tibialis anterior muscles. The number of interneurons in lumbar segments L4 (tibialis anterior) and L5 (soleus) was higher in both groups that stepped on the treadmill compared with control and was highest in rats that stepped at a 25° incline. In a majority of laminae, the distribution of total and muscle-specific activated interneurons was highest in the 25° incline group and lowest in the control group for both muscles. These data could reflect increased peripheral (proprioceptive) input as well as supraspinal drive associated with stepping and demonstrate the differences in 1) the activation of cholinergic interneurons near the central canal and 2) the laminar and segmental location of interneurons throughout the gray matter that play a role in generating stepping under different loading conditions in adult rats.
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Affiliation(s)
- Niranjala J K Tillakaratne
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, Los Angeles, California
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EphA4-mediated ipsilateral corticospinal tract misprojections are necessary for bilateral voluntary movements but not bilateral stereotypic locomotion. J Neurosci 2014; 34:5211-21. [PMID: 24719100 DOI: 10.1523/jneurosci.4848-13.2014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
In this study, we took advantage of the reported role of EphA4 in determining the contralateral spinal projection of the corticospinal tract (CST) to investigate the effects of ipsilateral misprojections on voluntary movements and stereotypic locomotion. Null EphA4 mutations produce robust ipsilateral CST misprojections, resulting in bilateral corticospinal tracts. We hypothesize that a unilateral voluntary limb movement, not a stereotypic locomotor movement, will become a bilateral movement in EphA4 knock-out mice with a bilateral CST. However, in EphA4 full knock-outs, spinal interneurons also develop bilateral misprojections. Aberrant bilateral spinal circuits could thus transform unilateral corticospinal control signals into bilateral movements. We therefore studied mice with conditional forebrain deletion of the EphA4 gene under control by Emx1, a gene expressed in the forebrain that affects the developing CST but spares brainstem motor pathways and spinal motor circuits. We examined two conditional knock-outs targeting forebrain EphA4 during performance of stereotypic locomotion and voluntary movement: adaptive locomotion over obstacles and exploratory reaching. We found that the conditional knock-outs used alternate stepping, not hopping, during overground locomotion, suggesting normal central pattern generator function and supporting our hypothesis of minimal CST involvement in the moment-to-moment control of stereotypic locomotion. In contrast, the conditional knock-outs showed bilateral voluntary movements under conditions when single limb movements are normally produced and, as a basis for this aberrant control, developed a bilateral motor map in motor cortex that is driven by the aberrant ipsilateral CST misprojections. Therefore, a specific change in CST connectivity is associated with and explains a change in voluntary movement.
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33
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Finkel E, Etlin A, Cherniak M, Mor Y, Lev-Tov A, Anglister L. Neuroanatomical basis for cholinergic modulation of locomotor networks by sacral relay neurons with ascending lumbar projections. J Comp Neurol 2014; 522:3437-55. [DOI: 10.1002/cne.23613] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 04/10/2014] [Accepted: 04/14/2014] [Indexed: 12/28/2022]
Affiliation(s)
- Eran Finkel
- Department of Medical Neurobiology, IMRIC; Hebrew University-Hadassah Medical School; Jerusalem 91120 Israel
| | - Alex Etlin
- Department of Medical Neurobiology, IMRIC; Hebrew University-Hadassah Medical School; Jerusalem 91120 Israel
| | - Meir Cherniak
- Department of Medical Neurobiology, IMRIC; Hebrew University-Hadassah Medical School; Jerusalem 91120 Israel
| | - Yoav Mor
- Department of Medical Neurobiology, IMRIC; Hebrew University-Hadassah Medical School; Jerusalem 91120 Israel
| | - Aharon Lev-Tov
- Department of Medical Neurobiology, IMRIC; Hebrew University-Hadassah Medical School; Jerusalem 91120 Israel
| | - Lili Anglister
- Department of Medical Neurobiology, IMRIC; Hebrew University-Hadassah Medical School; Jerusalem 91120 Israel
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34
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Zhang L, Kaneko S, Kikuchi K, Sano A, Maeda M, Kishino A, Shibata S, Mukaino M, Toyama Y, Liu M, Kimura T, Okano H, Nakamura M. Rewiring of regenerated axons by combining treadmill training with semaphorin3A inhibition. Mol Brain 2014; 7:14. [PMID: 24618249 PMCID: PMC4008261 DOI: 10.1186/1756-6606-7-14] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 02/12/2014] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Rats exhibit extremely limited motor function recovery after total transection of the spinal cord (SCT). We previously reported that SM-216289, a semaphorin3A inhibitor, enhanced axon regeneration and motor function recovery in SCT adult rats. However, these effects were limited because most regenerated axons likely do not connect to the right targets. Thus, rebuilding the appropriate connections for regenerated axons may enhance recovery. In this study, we combined semaphorin3A inhibitor treatment with extensive treadmill training to determine whether combined treatment would further enhance the "rewiring" of regenerated axons. In this study, which aimed for clinical applicability, we administered a newly developed, potent semaphorin3A inhibitor, SM-345431 (Vinaxanthone), using a novel drug delivery system that enables continuous drug delivery over the period of the experiment. RESULTS Treatment with SM-345431 using this delivery system enhanced axon regeneration and produced significant, but limited, hindlimb motor function recovery. Although extensive treadmill training combined with SM-345431 administration did not further improve axon regeneration, hindlimb motor performance was restored, as evidenced by the significant improvement in the execution of plantar steps on a treadmill. In contrast, control SCT rats could not execute plantar steps at any point during the experimental period. Further analyses suggested that this strategy reinforced the wiring of central pattern generators in lumbar spinal circuits, which, in turn, led to enhanced motor function recovery (especially in extensor muscles). CONCLUSIONS This study highlights the importance of combining treatments that promote axon regeneration with specific and appropriate rehabilitations that promote rewiring for the treatment of spinal cord injury.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Hideyuki Okano
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
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Guseva D, Loers G, Schachner M. Function-triggering antibodies to the adhesion molecule L1 enhance recovery after injury of the adult mouse femoral nerve. PLoS One 2014; 9:e112984. [PMID: 25393007 PMCID: PMC4231121 DOI: 10.1371/journal.pone.0112984] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 10/19/2014] [Indexed: 02/05/2023] Open
Abstract
L1 is among the few adhesion molecules that favors repair after trauma in the adult central nervous system of vertebrates by promoting neuritogenesis and neuronal survival, among other beneficial features. In the peripheral nervous system, L1 is up-regulated in Schwann cells and regrowing axons after nerve damage, but the functional consequences of this expression remain unclear. Our previous study of L1-deficient mice in a femoral nerve injury model showed an unexpected improved functional recovery, attenuated motoneuronal cell death, and enhanced Schwann cell proliferation, being attributed to the persistent synthesis of neurotrophic factors. On the other hand, transgenic mice over-expressing L1 in neurons led to improved remyelination, but not improved functional recovery. The present study was undertaken to investigate whether the monoclonal L1 antibody 557 that triggers beneficial L1 functions in vitro would trigger these also in femoral nerve repair. We analyzed femoral nerve regeneration in C57BL/6J mice that received this antibody in a hydrogel filled conduit connecting the cut and sutured nerve before its bifurcation, leading to short-term release of antibody by diffusion. Video-based quantitative analysis of motor functions showed improved recovery when compared to mice treated with conduits containing PBS in the hydrogel scaffold, as a vehicle control. This improved recovery was associated with attenuated motoneuron loss, remyelination and improved precision of preferential motor reinnervation. We suggest that function-triggering L1 antibodies applied to the lesion site at the time of injury over a limited time period will not only be beneficial in peripheral, but also central nervous system regeneration.
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Affiliation(s)
- Daria Guseva
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Gabriele Loers
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Melitta Schachner
- Center for Neuroscience, Shantou University Medical College, Shantou, China
- W. M. Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, United States of America
- * E-mail:
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Foster JD, Dunford C, Sillar KT, Miles GB. Nitric oxide-mediated modulation of the murine locomotor network. J Neurophysiol 2013; 111:659-74. [PMID: 24259545 PMCID: PMC3921400 DOI: 10.1152/jn.00378.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Spinal motor control networks are regulated by neuromodulatory systems to allow adaptability of movements. The present study aimed to elucidate the role of nitric oxide (NO) in the modulation of mammalian spinal locomotor networks. This was investigated with isolated spinal cord preparations from neonatal mice in which rhythmic locomotor-related activity was induced pharmacologically. Bath application of the NO donor diethylamine NONOate (DEA/NO) decreased the frequency and modulated the amplitude of locomotor-related activity recorded from ventral roots. Removal of endogenous NO with coapplication of a NO scavenger (PTIO) and a nitric oxide synthase (NOS) blocker [nitro-l-arginine methyl ester (l-NAME)] increased the frequency and decreased the amplitude of locomotor-related activity. This demonstrates that endogenously derived NO can modulate both the timing and intensity of locomotor-related activity. The effects of DEA/NO were mimicked by the cGMP analog 8-bromo-cGMP. In addition, the soluble guanylyl cyclase (sGC) inhibitor ODQ blocked the effects of DEA/NO on burst amplitude and frequency, although the frequency effect was only blocked at low concentrations of DEA/NO. This suggests that NO-mediated modulation involves cGMP-dependent pathways. Sources of NO were studied within the lumbar spinal cord during postnatal development (postnatal days 1–12) with NADPH-diaphorase staining. NOS-positive cells in the ventral horn exhibited a rostrocaudal gradient, with more cells in rostral segments. The number of NOS-positive cells was also found to increase during postnatal development. In summary, we have shown that NO, derived from sources within the mammalian spinal cord, modulates the output of spinal motor networks and is therefore likely to contribute to the fine-tuning of locomotor behavior.
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Affiliation(s)
- Joshua D Foster
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, United Kingdom
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The how and why of arm swing during human walking. Gait Posture 2013; 38:555-62. [PMID: 23489950 DOI: 10.1016/j.gaitpost.2013.02.006] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Revised: 11/26/2012] [Accepted: 02/05/2013] [Indexed: 02/02/2023]
Abstract
Humans walk bipedally, and thus, it is unclear why they swing their arms. In this paper, we will review the mechanisms and functions of arm swinging in human gait. First, we discuss the potential advantages of having swinging arms. Second, we go into the detail on the debate whether arm swing is arising actively or passively, where we will conclude that while a large part of arm swinging is mechanically passive, there is an active contribution of muscles (i.e. an activity that is not merely caused by stretch reflexes). Third, we describe the possible function of the active muscular contribution to arm swinging in normal gait, and discuss the possibility that a Central Pattern Generator (CPG) generates this activity. Fourth, we discuss examples from pathological cases, in which arm swinging is affected. Moreover, using the ideas presented, we suggest ways in which arm swing may be used as a therapeutic aid. We conclude that (1) arm swing should be seen as an integral part of human bipedal gait, arising mostly from passive movements, which are stabilized by active muscle control, which mostly originates from locomotor circuits in the central nervous system (2) arm swinging during normal bipedal gait most likely serves to reduce energy expenditure and (3) arm swinging may be of therapeutic value.
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Witts EC, Zagoraiou L, Miles GB. Anatomy and function of cholinergic C bouton inputs to motor neurons. J Anat 2013; 224:52-60. [PMID: 23701140 DOI: 10.1111/joa.12063] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2013] [Indexed: 12/11/2022] Open
Abstract
Motor control circuitry of the central nervous system must be flexible so that motor behaviours can be adapted to suit the varying demands of different states, developmental stages, and environments. Flexibility in motor control is largely provided by neuromodulatory systems which can adjust the output of motor circuits by modulating the properties and connectivity of neurons within them. The spinal circuitry which controls locomotion is subject to a range of neuromodulatory influences, including some which are intrinsic to the spinal cord. One such intrinsic neuromodulatory system, for which a wealth of anatomical information has recently been combined with new physiological data, is the C bouton system. C boutons are large, cholinergic inputs to motor neurons which were first described over 40 years ago but whose source and function have until recently remained a mystery. In this review we discuss how the convergence of anatomical, molecular genetic and physiological data has recently led to significant advances in our understanding of this unique neuromodulatory system. We also highlight evidence that C boutons are involved in spinal cord injury and disease, revealing their potential as targets for novel therapeutic strategies.
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Affiliation(s)
- Emily C Witts
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, UK
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Using motor behavior during an early critical period to restore skilled limb movement after damage to the corticospinal system during development. J Neurosci 2012; 32:9265-76. [PMID: 22764234 DOI: 10.1523/jneurosci.1198-12.2012] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
This study investigated the requirements for restoring motor function after corticospinal (CS) system damage during early postnatal development. Activity-dependent competition between the CS tracts (CSTs) of the two hemispheres is imperative for normal development. Blocking primary motor cortex (M1) activity unilaterally during a critical period [postnatal week 5 (PW5) to PW7] produces permanent contralateral motor skill impairments, loss of M1 motor map, aberrant CS terminations, and decreases in CST presynaptic sites and spinal cholinergic interneuron numbers. To repair these motor systems impairments and restore function, we manipulated motor experience in three groups of cats after this CST injury produced by inactivation. One group wore a jacket restraining the limb ipsilateral to inactivation, forcing use of the contralateral, impaired limb, for the month after M1 inactivation (PW8-PW13; "restraint alone"). A second group wore the restraint during PW8-PW13 and was also trained for 1 h/d in a reaching task with the contralateral forelimb ("early training"). To test the efficacy of intervention during adolescence, a third group wore the restraint and received reach training during PW20-PW24 ("delayed training"). Early training restored CST connections and the M1 motor map, increased cholinergic spinal interneurons numbers on the contralateral, relative to ipsilateral, side, and abrogated limb control impairments. Delayed training restored CST connectivity and the M1 motor map but not contralateral spinal cholinergic cell counts or motor performance. Restraint alone only restored CST connectivity. Our findings stress the need to reestablish the integrated functions of the CS system at multiple hierarchical levels in restoring skilled motor function after developmental injury.
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Coulon P, Bras H, Vinay L. Characterization of last-order premotor interneurons by transneuronal tracing with rabies virus in the neonatal mouse spinal cord. J Comp Neurol 2012; 519:3470-87. [PMID: 21800300 DOI: 10.1002/cne.22717] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We characterized the interneurons involved in the control of ankle extensor (triceps surae [TS] muscles) motoneurons (MNs) in the lumbar enlargement of mouse neonates by retrograde transneuronal tracing using rabies virus (RV). Examination of the kinetics of retrograde transneuronal transfer at sequential intervals post inoculation enabled us to determine the time window during which only the first-order interneurons, i.e., interneurons likely monosynaptically connected to MNs (last-order interneurons [loINs]) were RV-infected. The infection of the network resulted exclusively from a retrograde transport of RV along the motor pathway. About 80% of the loINs were observed ipsilaterally to the injection. They were distributed all along the lumbar enlargement, but the majority was observed in L4 and L5 segments where TS MNs were localized. Most loINs were distributed in laminae V-VII, whereas the most superficial laminae were devoid of RV infection. Contralaterally, commissural loINs were found essentially in lamina VIII of all lumbar segments. Groups of loINs were characterized by their chemical phenotypes using dual immunolabeling. Glycinergic neurons connected to TS MNs represented 50% of loINs ipsilaterally and 10% contralaterally. As expected, the ipsilateral glycinergic loINs included Renshaw cells, the most ventral neurons expressing calbindin. We also demonstrated a direct connection between a group of cholinergic interneurons observed ipsilaterally in L3 and the rostral part of L4, and TS MNs. To conclude, transneuronal tracing with RV, combined with an immunohistochemical detection of neuronal determinants, allows a very specific mapping of motor networks involved in the control of single muscles.
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Affiliation(s)
- Patrice Coulon
- Laboratoire Plasticité et Physio-Pathologie de la Motricité, Unité Mixte de Recherche 6196, Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Université, Marseille, France.
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Skup M, Gajewska-Wozniak O, Grygielewicz P, Mankovskaya T, Czarkowska-Bauch J. Different effects of spinalization and locomotor training of spinal animals on cholinergic innervation of the soleus and tibialis anterior motoneurons. Eur J Neurosci 2012; 36:2679-88. [PMID: 22708650 DOI: 10.1111/j.1460-9568.2012.08182.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cholinergic input modulates excitability of motoneurons and plays an important role in the control of locomotion in both intact and spinalized animals. However, spinal cord transection in adult rats affects cholinergic innervation of only some hindlimb motoneurons, suggesting that specificity of this response is related to functional differences between motoneurons. Our aim was therefore to compare cholinergic input to motoneurons innervating the soleus (Sol) and tibialis anterior (TA) motoneurons following spinal cord transection at a low-thoracic level. The second aim was to investigate whether deficits in cholinergic input to these motoneurons could be modified by locomotor training. The Sol and TA motoneurons were identified by retrograde labelling with fluorescent dyes injected intramuscularly. Cholinergic terminals were detected using anti-vesicular acetylcholine transporter (VAChT) antibody. Overall innervation of motoneurons was evaluated with anti-synaptophysin antibody. After spinalization we found a decrease in the number of VAChT-positive boutons apposing perikarya of the Sol (to 49%) but not TA motoneurons. Locomotor training, resulting in moderate functional improvement, partly reduced the deficit in cholinergic innervation of Sol motoneurons by increasing the number of VAChT-positive boutons. However, the optical density of VAChT-positive boutons terminating on various motoneurons, which decreased after spinalization, continued to decrease despite the training, suggesting an impairment of acetylcholine availability in the terminals. Different effects of spinal cord transection on cholinergic innervation of motoneurons controlling the ankle extensor and flexor muscles point to different functional states of these muscles in paraplegia as a possible source of activity-dependent signaling regulating cholinergic input to the motoneurons.
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Affiliation(s)
- Malgorzata Skup
- Department of Neurophysiology, Nencki Institute of Experimental Biology, Warsaw, Poland.
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Kapitza S, Zörner B, Weinmann O, Bolliger M, Filli L, Dietz V, Schwab ME. Tail spasms in rat spinal cord injury: changes in interneuronal connectivity. Exp Neurol 2012; 236:179-89. [PMID: 22569103 DOI: 10.1016/j.expneurol.2012.04.023] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2012] [Revised: 04/16/2012] [Accepted: 04/23/2012] [Indexed: 12/16/2022]
Abstract
Uncontrolled muscle spasms often develop after spinal cord injury. Structural and functional maladaptive changes in spinal neuronal circuits below the lesion site were postulated as an underlying mechanism but remain to be demonstrated in detail. To further explore the background of such secondary phenomena, rats received a complete sacral spinal cord transection at S(2) spinal level. Animals progressively developed signs of tail spasms starting 1 week after injury. Immunohistochemistry was performed on S(3/4) spinal cord sections from intact rats and animals were sacrificed 1, 4 and 12 weeks after injury. We found a progressive decrease of cholinergic input onto motoneuron somata starting 1 week post-lesion succeeded by shrinkage of the cholinergic interneuron cell bodies located around the central canal. The number of inhibitory GABAergic boutons in close contact with Ia afferent fibers was greatly reduced at 1 week after injury, potentially leading to a loss of inhibitory control of the Ia stretch reflex pathways. In addition, a gradual loss and shrinkage of GAD65 positive GABAergic cell bodies was detected in the medial portion of the spinal cord gray matter. These results show that major structural changes occur in the connectivity of the sacral spinal cord interneuronal circuits below the level of transection. They may contribute in an important way to the development of spastic symptoms after spinal cord injury, while reduced cholinergic input on motoneurons is assumed to result in the rapid exhaustion of the central drive required for the performance of locomotor movements in animals and humans.
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Affiliation(s)
- Sandra Kapitza
- Brain Research Institute, University and ETH Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Miles GB, Sillar KT. Neuromodulation of Vertebrate Locomotor Control Networks. Physiology (Bethesda) 2011; 26:393-411. [DOI: 10.1152/physiol.00013.2011] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vertebrate locomotion must be adaptable in light of changing environmental, organismal, and developmental demands. Much of the underlying flexibility in the output of central pattern generating (CPG) networks of the spinal cord and brain stem is endowed by neuromodulation. This review provides a synthesis of current knowledge on the way that various neuromodulators modify the properties of and connections between CPG neurons to sculpt CPG network output during locomotion.
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Affiliation(s)
- Gareth B. Miles
- School of Biology, University of St. Andrews, St. Andrews, Scotland, United Kingdom
| | - Keith T. Sillar
- School of Biology, University of St. Andrews, St. Andrews, Scotland, United Kingdom
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Bertrand SS, Cazalets JR. Cholinergic partition cells and lamina x neurons induce a muscarinic-dependent short-term potentiation of commissural glutamatergic inputs in lumbar motoneurons. Front Neural Circuits 2011; 5:15. [PMID: 22069380 PMCID: PMC3208176 DOI: 10.3389/fncir.2011.00015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 10/13/2011] [Indexed: 01/08/2023] Open
Abstract
Acetylcholine and the activation of muscarinic receptors influence the activity of neural networks generating locomotor behavior in the mammalian spinal cord. Using electrical stimulations of the ventral commissure, we show that commissural muscarinic (CM) depolarizations could be induced in lumbar motoneurons. We provide a detailed electrophysiological characterization of the muscarinic receptors and the membrane conductance involved in these responses. Activation of the CM terminals, originating from lamina X neurons and partition cells, induced a pathway-specific short-term potentiation (STP) of commissural glutamatergic inputs in motoneurons. This STP is occluded in the presence of the muscarinic antagonist atropine. During fictive locomotion, the activation of the commissural pathways transiently enhanced the motor output in a muscarinic-dependent manner. This study describes for the first time a novel regulatory mechanism of synaptic strength in spinal locomotor networks. Such cellular mechanisms would endow the locomotor central pattern generators with adaptive processes needed to generate appropriate synaptic inputs to motoneurons during different motor tasks.
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Auyong N, Ollivier-Lanvin K, Lemay MA. Population spatiotemporal dynamics of spinal intermediate zone interneurons during air-stepping in adult spinal cats. J Neurophysiol 2011; 106:1943-53. [PMID: 21775722 DOI: 10.1152/jn.00258.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The lumbar spinal cord circuitry can autonomously generate locomotion, but it remains to be determined which types of neurons constitute the locomotor generator and how their population activity is organized spatially in the mammalian spinal cord. In this study, we investigated the spatiotemporal dynamics of the spinal interneuronal population activity in the intermediate zone of the adult mammalian cord. Segmental interneuronal population activity was examined via multiunit activity (MUA) during air-stepping initiated by perineal stimulation in subchronic spinal cats. In contrast to single-unit activity, MUA provides a continuous measure of neuronal activity within a ∼100-μm volume around the recording electrode. MUA was recorded during air-stepping, along with hindlimb muscle activity, from segments L3 to L7 with two multichannel electrode arrays placed into the left and right hemicord intermediate zones (lamina V-VII). The phasic modulation and spatial organization of MUA dynamics were examined in relation to the locomotor cycle. Our results show that segmental population activity is modulated with respect to the ipsilateral step cycle during air-stepping, with maximal activity occurring near the ipsilateral swing to stance transition period. The phase difference between the population activity within the left and right hemicords was also found to correlate to the left-right alternation of the step cycle. Furthermore, examination of MUA throughout the rostrocaudal extent showed no differences in population dynamics between segmental levels, suggesting that the spinal interneurons targeted in this study may operate as part of a distributed "clock" mechanism rather than a rostrocaudal oscillation as seen with motoneuronal activity.
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Affiliation(s)
- Nicholas Auyong
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
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Hwang IK, Yoo DY, Yoo KY, Choi JH, Lee HJ, Lee CH, Moon SM, Lee YL, Shin HC, Won MH. Microtubule associated protein 2 and choline acetyltransferase immunoreactivity in the lumbar spinal cord of young adult and aged dogs. Res Vet Sci 2011; 91:e10-5. [PMID: 21435670 DOI: 10.1016/j.rvsc.2011.02.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 01/09/2011] [Accepted: 02/25/2011] [Indexed: 10/18/2022]
Abstract
German Shepherds are a good model for research about aging and neurological disorders such as lumbosacral spinal canal stenosis. We compared neurons, glia and cholinergic neurons in the ventral horn of the lumbar spinal cord (L(3)) between adult (1-2 years old) and aged (10-12 years old) groups. Any pathological findings were not found by hematoxylin and eosin staining and neurological examination, and the number of NeuN (a marker for neurons)-positive neurons were similar in both groups. Microtubule-associated protein 2 (MAP2) immunoreactive dendrites in the aged dog were decreased without any change in β-tubulin protein level. Glial fibrillary acidic protein (a marker for astrocytes) and ionized calcium-binding adapter molecule 1 (a marker for microglia) immunoreactivity were not significantly changed in both groups. The number of ChAT immunoreactive neurons was decreased; however, its protein level was not significantly changed in the aged group. These results suggest that numbers of ventral horn neurons are not changed, but cholinergic neurons may change in aged dogs compared to adult dogs.
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Affiliation(s)
- I K Hwang
- Department of Anatomy and Cell Biology, College of Veterinary Medicine, Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, South Korea
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Noga BR, Johnson DMG, Riesgo MI, Pinzon A. Locomotor-activated neurons of the cat. II. Noradrenergic innervation and colocalization with NEα 1a or NEα 2b receptors in the thoraco-lumbar spinal cord. J Neurophysiol 2011; 105:1835-49. [PMID: 21307324 DOI: 10.1152/jn.00342.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Norepinephrine (NE) is a strong modulator and/or activator of spinal locomotor networks. Thus noradrenergic fibers likely contact neurons involved in generating locomotion. The aim of the present study was to investigate the noradrenergic innervation of functionally related, locomotor-activated neurons within the thoraco-lumbar spinal cord. This was accomplished by immunohistochemical colocalization of noradrenergic fibers using dopamine-β-hydroxylase or NEα(1A) and NEα(2B) receptors with cells expressing the c-fos gene activity-dependent marker Fos. Experiments were performed on paralyzed, precollicular-postmamillary decerebrate cats, in which locomotion was induced by electrical stimulation of the mesencephalic locomotor region. The majority of Fos labeled neurons, especially abundant in laminae VII and VIII throughout the thoraco-lumbar (T13-L7) region of locomotor animals, showed close contacts with multiple noradrenergic boutons. A small percentage (10-40%) of Fos neurons in the T7-L7 segments showed colocalization with NEα(1A) receptors. In contrast, NEα(2B) receptor immunoreactivity was observed in 70-90% of Fos cells, with no obvious rostrocaudal gradient. In comparison with results obtained from our previous study on the same animals, a significantly smaller proportion of Fos labeled neurons were innervated by noradrenergic than serotonergic fibers, with significant differences observed for laminae VII and VIII in some segments. In lamina VII of the lumbar segments, the degree of monoaminergic receptor subtype/Fos colocalization examined statistically generally fell into the following order: NEα(2B) = 5-HT(2A) ≥ 5-HT(7) = 5-HT(1A) > NEα(1A). These results suggest that noradrenergic modulation of locomotion involves NEα(1A)/NEα(2B) receptors on noradrenergic-innervated locomotor-activated neurons within laminae VII and VIII of thoraco-lumbar segments. Further study of the functional role of these receptors in locomotion is warranted.
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Affiliation(s)
- Brian R Noga
- The Miami Project to Cure Paralysis, University of Miami School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA.
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AuYong N, Ollivier-Lanvin K, Lemay MA. Preferred locomotor phase of activity of lumbar interneurons during air-stepping in subchronic spinal cats. J Neurophysiol 2010; 105:1011-22. [PMID: 21084683 DOI: 10.1152/jn.00523.2010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spinal locomotor circuits are intrinsically capable of driving a variety of behaviors such as stepping, scratching, and swimming. Based on an observed rostrocaudal wave of activity in the motoneuronal firing during locomotor tasks, the traveling-wave hypothesis proposes that spinal interneuronal firing follows a similar rostrocaudal pattern of activation, suggesting the presence of spatially organized interneuronal modules within the spinal motor system. In this study, we examined if the spatial organization of the lumbar interneuronal activity patterns during locomotor activity in the adult mammalian spinal cord was consistent with a traveling-wave organizational scheme. The activity of spinal interneurons within the lumbar intermediate zone was examined during air-stepping in subchronic spinal cats. The preferred phase of interneuronal activity during a step cycle was determined using circular statistics. We found that the preferred phases of lumbar interneurons from both sides of the cord were evenly distributed over the entire step cycle with no indication of functional groupings. However, when units were subcategorized according to spinal hemicords, the preferred phases of units on each side largely fell around the period of extensor muscle activity on each side. In addition, there was no correlation between the preferred phases of units and their rostrocaudal locations along the spinal cord with preferred phases corresponding to both flexion and extension phases of the step cycle found at every rostrocaudal level of the cord. These results are consistent with the hypothesis that interneurons operate as part of a longitudinally distributed network rather than a rostrocaudally organized traveling-wave network.
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Affiliation(s)
- Nicholas AuYong
- Drexel University College of Medicine, Department of Neurobiology and Anatomy, 2900 W. Queen Lane, Philadelphia, PA 19129, USA
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Liu TT, Bannatyne BA, Maxwell DJ. Organization and neurochemical properties of intersegmental interneurons in the lumbar enlargement of the adult rat. Neuroscience 2010; 171:461-84. [PMID: 20849930 DOI: 10.1016/j.neuroscience.2010.09.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 09/06/2010] [Accepted: 09/08/2010] [Indexed: 02/05/2023]
Abstract
Intersegmental interneurons with relatively short axons perform an important role in the coordination of limb movement but surprisingly little is known about their organization and how they contribute to neuronal networks in the adult rat. We undertook a series of anatomical tract-tracing studies to label cell bodies and axons of intersegmental neurons in the lumbar cord and characterized their neurochemical properties by using immunocytochemistry. The b-subunit of cholera toxin was injected into L1 or L3 segments of seven rats in the vicinity of lateral or medial motor nuclei. In L5 lumbar segments, cells were found to be concentrated in contralateral lamina VIII, and in ipsilateral lamina VII and laminae V-VI following injections into the lateral and medial motor nuclei respectively. About 25% of labelled cells contained calbindin or calretinin or a combination of both. Calbindin positive cells were mainly distributed within the ipsilateral side of the L5 segment, especially within the ipsilateral dorsal horn whereas there was a concentration of calretinin cells in contralateral lamina VIII. A small population of cells around the central canal were cholinergic. We also examined axon terminals that projected from L1/3 to the L5 contralateral lateral motor nucleus. The majority of these axons were excitatory (75%) and made direct contacts with motoneurons. However, most inhibitory axons in L5 contained a mixture of GABA and glycine (20%) and about 22% of the total population of axons contained calbindin. In contrast, 19% of all intra-segmental axons in the L3 contralateral lateral motor nucleus were found to be purely glycinergic and 17% contained a mixture of GABA and glycine. This study shows that short range interneurons form extensive ipsi- and contralateral projections within the lumbar enlargement and that many of them contain calcium binding proteins. Those projecting contralaterally to motor nuclei are predominantly excitatory.
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Affiliation(s)
- T T Liu
- Spinal Cord Group, Institute of Neuroscience and Psychology, College of Medicine, Veterinary Medicine and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
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Enjin A, Rabe N, Nakanishi ST, Vallstedt A, Gezelius H, Memic F, Lind M, Hjalt T, Tourtellotte WG, Bruder C, Eichele G, Whelan PJ, Kullander K. Identification of novel spinal cholinergic genetic subtypes disclose Chodl and Pitx2 as markers for fast motor neurons and partition cells. J Comp Neurol 2010; 518:2284-304. [PMID: 20437528 DOI: 10.1002/cne.22332] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Spinal cholinergic neurons are critical for motor function in both the autonomic and somatic nervous systems and are affected in spinal cord injury and in diseases such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy. Using two screening approaches and in situ hybridization, we identified 159 genes expressed in typical cholinergic patterns in the spinal cord. These include two general cholinergic neuron markers, one gene exclusively expressed in motor neurons, and nine genes expressed in unknown subtypes of somatic motor neurons. Further, we present evidence that chondrolectin (Chodl) is expressed by fast motor neurons and that estrogen-related receptor beta (ERRbeta) is a candidate marker for slow motor neurons. In addition, we suggest paired-like homeodomain transcription factor 2 (Pitx2) as a marker for cholinergic partition cells.
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Affiliation(s)
- Anders Enjin
- Department of Neuroscience, Uppsala University, 751 23 Uppsala, Sweden
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