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Spinal Cord Circuits: Models and Reality. NEUROPHYSIOLOGY+ 2022. [DOI: 10.1007/s11062-022-09927-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Vivacqua G, Biagioni F, Busceti CL, Ferrucci M, Madonna M, Ryskalin L, Yu S, D'Este L, Fornai F. Motor Neurons Pathology After Chronic Exposure to MPTP in Mice. Neurotox Res 2019; 37:298-313. [PMID: 31721049 DOI: 10.1007/s12640-019-00121-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 09/18/2019] [Accepted: 09/25/2019] [Indexed: 12/12/2022]
Abstract
The neurotoxin 1-methyl,4-phenyl-1,2,3,6-tetrahydropiridine (MPTP) is widely used to produce experimental parkinsonism in rodents and primates. Among different administration protocols, continuous or chronic exposure to small amounts of MPTP is reported to better mimic cell pathology reminiscent of Parkinson's disease (PD). Catecholamine neurons are the most sensitive to MPTP neurotoxicity; however, recent studies have found that MPTP alters the fine anatomy of the spinal cord including motor neurons, thus overlapping again with the spinal cord involvement documented in PD. In the present study, we demonstrate that chronic exposure to low amounts of MPTP (10 mg/kg daily, × 21 days) significantly reduces motor neurons in the ventral lumbar spinal cord while increasing α-synuclein immune-staining within the ventral horn. Spinal cord involvement in MPTP-treated mice extends to Calbindin D28 KDa immune-reactive neurons other than motor neurons within lamina VII. These results were obtained in the absence of significant reduction of dopaminergic cell bodies in the Substantia Nigra pars compacta, while a slight decrease was documented in striatal tyrosine hydroxylase immune-staining. Thus, the present study highlights neuropathological similarities between dopaminergic neurons and spinal motor neurons and supports the pathological involvement of spinal cord in PD and experimental MPTP-induced parkinsonism. Remarkably, the toxic threshold for motor neurons appears to be lower compared with nigral dopaminergic neurons following a chronic pattern of MPTP intoxication. This sharply contrasts with previous studies showing that MPTP intoxication produces comparable neuronal loss within spinal cord and Substantia Nigra.
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Affiliation(s)
- Giorgio Vivacqua
- Department of Anatomy, Histology, Forensic Medicine and Locomotor Sciences, Via A. Borelli 50, 00161, Rome, Italy
- Department of Neurobiology, Xuan Wu Hospital, Capital University of Medical Sciences, 45 Changchun St, Beijing, 100053, China
| | | | | | - Michela Ferrucci
- Department of Traslational Research and New Technologies in Medicine and Surgery, University of Pisa, via Roma 55, 56126, Pisa, Italy
| | | | - Larisa Ryskalin
- Department of Traslational Research and New Technologies in Medicine and Surgery, University of Pisa, via Roma 55, 56126, Pisa, Italy
| | - Shun Yu
- Department of Neurobiology, Xuan Wu Hospital, Capital University of Medical Sciences, 45 Changchun St, Beijing, 100053, China
| | - Loredana D'Este
- Department of Anatomy, Histology, Forensic Medicine and Locomotor Sciences, Via A. Borelli 50, 00161, Rome, Italy
| | - Francesco Fornai
- I.R.C.C.S. Neuromed, Via Atinense, 18, Pozzilli, Italy.
- Department of Traslational Research and New Technologies in Medicine and Surgery, University of Pisa, via Roma 55, 56126, Pisa, Italy.
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Hoang PT, Chalif JI, Bikoff JB, Jessell TM, Mentis GZ, Wichterle H. Subtype Diversification and Synaptic Specificity of Stem Cell-Derived Spinal Interneurons. Neuron 2019; 100:135-149.e7. [PMID: 30308166 DOI: 10.1016/j.neuron.2018.09.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 07/06/2018] [Accepted: 09/09/2018] [Indexed: 12/25/2022]
Abstract
Neuronal diversification is a fundamental step in the construction of functional neural circuits, but how neurons generated from single progenitor domains acquire diverse subtype identities remains poorly understood. Here we developed an embryonic stem cell (ESC)-based system to model subtype diversification of V1 interneurons, a class of spinal neurons comprising four clades collectively containing dozens of molecularly distinct neuronal subtypes. We demonstrate that V1 subtype diversity can be modified by extrinsic signals. Inhibition of Notch and activation of retinoid signaling results in a switch to MafA clade identity and enriches differentiation of Renshaw cells, a specialized MafA subtype that mediates recurrent inhibition of spinal motor neurons. We show that Renshaw cells are intrinsically programmed to migrate to species-specific laminae upon transplantation and to form subtype-specific synapses with motor neurons. Our results demonstrate that stem cell-derived neuronal subtypes can be used to investigate mechanisms underlying neuronal subtype specification and circuit assembly.
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Affiliation(s)
- Phuong T Hoang
- Departments of Pathology and Cell Biology, Neuroscience, Rehabilitation & Regenerative Medicine, and Neurology, Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Joshua I Chalif
- Departments of Pathology and Cell Biology and Neurology, Center for Motor Neuron Biology and Disease, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jay B Bikoff
- Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Thomas M Jessell
- Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - George Z Mentis
- Departments of Pathology and Cell Biology and Neurology, Center for Motor Neuron Biology and Disease, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Hynek Wichterle
- Departments of Pathology and Cell Biology, Neuroscience, Rehabilitation & Regenerative Medicine, and Neurology, Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia University Irving Medical Center, New York, NY 10032, USA.
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Iizuka M, Ikeda K, Onimaru H, Izumizaki M. Expressions of VGLUT1/2 in the inspiratory interneurons and GAD65/67 in the inspiratory Renshaw cells in the neonatal rat upper thoracic spinal cord. IBRO Rep 2018; 5:24-32. [PMID: 30135953 PMCID: PMC6095097 DOI: 10.1016/j.ibror.2018.08.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 08/01/2018] [Indexed: 01/06/2023] Open
Abstract
About half of the inspiratory interneurons in the ventromedial area of the third thoracic segment are glutamatergic. These glutamatergic interneurons may enhance the inspiratory intercostal motor activity. Inspiratory Renshaw cells exist in the ventromedial area of the third thoracic segments. Most of these Renshaw cells are GABAergic, and cause a single spike followed by ventral root stimulation at neonatal stage.
Although the inspiratory spinal interneurons are thought to provide a major fraction of the excitatory synaptic potentials to the inspiratory intercostal motoneurons, this has not been confirmed. To clarify whether some inspiratory spinal interneurons are glutamatergic, we obtained whole-cell recordings from the ventromedial area of the third thoracic segments in an isolated brainstem-spinal cord preparation from neonatal rat, and the recorded cells were filled with Lucifer Yellow for later visualization. We then examined the existence of mRNA of vesicular glutamate transporters 1 and/or 2 (VGLUT1/2) by performing in situ hybridization. To discriminate the interneurons from motoneurons, we electrically stimulated the third thoracic ventral root on the recorded side, and the results verified that the antidromic spike or excitatory postsynaptic potential was not evoked. In cases in which the ventral root stimulation evoked depolarizing postsynaptic potentials, we examined the existence of glutamic acid decarboxylase 65 and/or 67 (GAD65/67) mRNA using a mixed probe to verify whether the cell was truly a Renshaw cell. The long diameter of the recorded interneurons was 22 ± 8 μm; the short diameter was 13 ± 4 μm. The interneurons' input resistance was 598 ± 274 MΩ. The Renshaw cells had similar sizes and input resistance. Six of 11 interneurons expressed VGLUT1/2, and four of five Renshaw cells expressed GAD65/67. Our findings suggest that approximately one-half of the inspiratory interneurons in the ventromedial area of the neonatal rat thoracic spinal cord are glutamatergic, and these interneurons might enhance the inspiratory intercostal motor activity.
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Affiliation(s)
- Makito Iizuka
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
| | - Keiko Ikeda
- Department of Physiology, School of Medicine, International University of Health and Welfare, Narita Campus 4-3 Kozunomori, Narita-shi, Chiba, 286-8686, Japan.,Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, 329-0498, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
| | - Masahiko Izumizaki
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
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Côté MP, Murray LM, Knikou M. Spinal Control of Locomotion: Individual Neurons, Their Circuits and Functions. Front Physiol 2018; 9:784. [PMID: 29988534 PMCID: PMC6026662 DOI: 10.3389/fphys.2018.00784] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 06/05/2018] [Indexed: 12/31/2022] Open
Abstract
Systematic research on the physiological and anatomical characteristics of spinal cord interneurons along with their functional output has evolved for more than one century. Despite significant progress in our understanding of these networks and their role in generating and modulating movement, it has remained a challenge to elucidate the properties of the locomotor rhythm across species. Neurophysiological experimental evidence indicates similarities in the function of interneurons mediating afferent information regarding muscle stretch and loading, being affected by motor axon collaterals and those mediating presynaptic inhibition in animals and humans when their function is assessed at rest. However, significantly different muscle activation profiles are observed during locomotion across species. This difference may potentially be driven by a modified distribution of muscle afferents at multiple segmental levels in humans, resulting in an altered interaction between different classes of spinal interneurons. Further, different classes of spinal interneurons are likely activated or silent to some extent simultaneously in all species. Regardless of these limitations, continuous efforts on the function of spinal interneuronal circuits during mammalian locomotion will assist in delineating the neural mechanisms underlying locomotor control, and help develop novel targeted rehabilitation strategies in cases of impaired bipedal gait in humans. These rehabilitation strategies will include activity-based therapies and targeted neuromodulation of spinal interneuronal circuits via repetitive stimulation delivered to the brain and/or spinal cord.
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Affiliation(s)
- Marie-Pascale Côté
- CÔTÉ Lab, Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Lynda M. Murray
- Motor Control and NeuroRecovery Research Laboratory (Klab4Recovery), Department of Physical Therapy, College of Staten Island, City University of New York, New York, NY, United States
- Graduate Center, Ph.D. Program in Biology, City University of New York, New York, NY, United States
| | - Maria Knikou
- Motor Control and NeuroRecovery Research Laboratory (Klab4Recovery), Department of Physical Therapy, College of Staten Island, City University of New York, New York, NY, United States
- Graduate Center, Ph.D. Program in Biology, City University of New York, New York, NY, United States
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Floyd TL, Dai Y, Ladle DR. Characterization of calbindin D28k expressing interneurons in the ventral horn of the mouse spinal cord. Dev Dyn 2017; 247:185-193. [PMID: 29090497 DOI: 10.1002/dvdy.24601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 10/24/2017] [Accepted: 10/24/2017] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Expression of the calcium binding protein, calbindin (CB), is well established as a hallmark of Renshaw cells, a class of interneurons found in spatially restricted areas in the ventral spinal cord that directly modulate motor neuron activity. CB expression, however, is not restricted only to Renshaw cells in the ventral horn, and within this population other interneuron subtypes may be identifiable on the basis of cell position and the potential for coexpression of other calcium binding proteins. RESULTS Here we have quantified the changing CB expression pattern in the ventral spinal cord across postnatal development in the mouse. Fewer neurons express CB as postnatal development progresses, and those neurons frequently coexpress other calcium binding proteins (calretinin and parvalbumin) in subpopulations with distinct spatial distributions. We also found a significant portion of CB-expressing interneurons receive putative synaptic contacts from primary sensory afferents. CONCLUSIONS These findings suggest CB labels a heterogeneous group of interneurons in the ventral horn, some of which may process sensory information. Based on cellular position, CB expression may be a shared feature of subsets of interneurons arising from multiple ventral progenitor domains. Developmental Dynamics 247:185-193, 2018. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Taylor L Floyd
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio, USA
| | - Yiyun Dai
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio, USA
| | - David R Ladle
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio, USA
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Bikoff JB, Gabitto MI, Rivard AF, Drobac E, Machado TA, Miri A, Brenner-Morton S, Famojure E, Diaz C, Alvarez FJ, Mentis GZ, Jessell TM. Spinal Inhibitory Interneuron Diversity Delineates Variant Motor Microcircuits. Cell 2016; 165:207-219. [PMID: 26949184 DOI: 10.1016/j.cell.2016.01.027] [Citation(s) in RCA: 175] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 11/30/2015] [Accepted: 01/15/2016] [Indexed: 12/11/2022]
Abstract
Animals generate movement by engaging spinal circuits that direct precise sequences of muscle contraction, but the identity and organizational logic of local interneurons that lie at the core of these circuits remain unresolved. Here, we show that V1 interneurons, a major inhibitory population that controls motor output, fractionate into highly diverse subsets on the basis of the expression of 19 transcription factors. Transcriptionally defined V1 subsets exhibit distinct physiological signatures and highly structured spatial distributions with mediolateral and dorsoventral positional biases. These positional distinctions constrain patterns of input from sensory and motor neurons and, as such, suggest that interneuron position is a determinant of microcircuit organization. Moreover, V1 diversity indicates that different inhibitory microcircuits exist for motor pools controlling hip, ankle, and foot muscles, revealing a variable circuit architecture for interneurons that control limb movement.
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Affiliation(s)
- Jay B Bikoff
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA; Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
| | - Mariano I Gabitto
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA; Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Andre F Rivard
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30319, USA
| | - Estelle Drobac
- Center for Motor Neuron Biology and Disease, Departments of Pathology and Cell Biology and Neurology, Columbia University, New York, NY 10032, USA
| | - Timothy A Machado
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA; Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Andrew Miri
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA; Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Susan Brenner-Morton
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA; Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Erica Famojure
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA; Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Carolyn Diaz
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA; Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Francisco J Alvarez
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30319, USA
| | - George Z Mentis
- Center for Motor Neuron Biology and Disease, Departments of Pathology and Cell Biology and Neurology, Columbia University, New York, NY 10032, USA
| | - Thomas M Jessell
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA; Departments of Neuroscience and Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
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Gabitto MI, Pakman A, Bikoff JB, Abbott LF, Jessell TM, Paninski L. Bayesian Sparse Regression Analysis Documents the Diversity of Spinal Inhibitory Interneurons. Cell 2016; 165:220-233. [PMID: 26949187 DOI: 10.1016/j.cell.2016.01.026] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 11/30/2015] [Accepted: 01/15/2016] [Indexed: 12/14/2022]
Abstract
Documenting the extent of cellular diversity is a critical step in defining the functional organization of tissues and organs. To infer cell-type diversity from partial or incomplete transcription factor expression data, we devised a sparse Bayesian framework that is able to handle estimation uncertainty and can incorporate diverse cellular characteristics to optimize experimental design. Focusing on spinal V1 inhibitory interneurons, for which the spatial expression of 19 transcription factors has been mapped, we infer the existence of ~50 candidate V1 neuronal types, many of which localize in compact spatial domains in the ventral spinal cord. We have validated the existence of inferred cell types by direct experimental measurement, establishing this Bayesian framework as an effective platform for cell-type characterization in the nervous system and elsewhere.
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Affiliation(s)
- Mariano I Gabitto
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA.
| | - Ari Pakman
- Department of Statistics and Grossman Center for the Statistics of Mind, Columbia University, New York, NY 10027, USA
| | - Jay B Bikoff
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - L F Abbott
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Thomas M Jessell
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Liam Paninski
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Statistics and Grossman Center for the Statistics of Mind, Columbia University, New York, NY 10027, USA.
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Siembab VC, Gomez-Perez L, Rotterman TM, Shneider NA, Alvarez FJ. Role of primary afferents in the developmental regulation of motor axon synapse numbers on Renshaw cells. J Comp Neurol 2016; 524:1892-919. [PMID: 26660356 DOI: 10.1002/cne.23946] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 11/24/2015] [Accepted: 11/25/2015] [Indexed: 01/21/2023]
Abstract
Motor function in mammalian species depends on the maturation of spinal circuits formed by a large variety of interneurons that regulate motoneuron firing and motor output. Interneuron activity is in turn modulated by the organization of their synaptic inputs, but the principles governing the development of specific synaptic architectures unique to each premotor interneuron are unknown. For example, Renshaw cells receive, at least in the neonate, convergent inputs from sensory afferents (likely Ia) and motor axons, raising the question of whether they interact during Renshaw cell development. In other well-studied neurons, such as Purkinje cells, heterosynaptic competition between inputs from different sources shapes synaptic organization. To examine the possibility that sensory afferents modulate synaptic maturation on developing Renshaw cells, we used three animal models in which afferent inputs in the ventral horn are dramatically reduced (ER81(-/-) knockout), weakened (Egr3(-/-) knockout), or strengthened (mlcNT3(+/-) transgenic). We demonstrate that increasing the strength of sensory inputs on Renshaw cells prevents their deselection and reduces motor axon synaptic density, and, in contrast, absent or diminished sensory afferent inputs correlate with increased densities of motor axons synapses. No effects were observed on other glutamatergic inputs. We conclude that the early strength of Ia synapses influences their maintenance or weakening during later development and that heterosynaptic influences from sensory synapses during early development regulates the density and organization of motor inputs on mature Renshaw cells.
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Affiliation(s)
- Valerie C Siembab
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, 45435
| | - Laura Gomez-Perez
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, 30322
| | - Travis M Rotterman
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, 30322
| | - Neil A Shneider
- Department of Neurology, Center for Motor Neuron Biology and Disease, Columbia University, New York, New York, 10032
| | - Francisco J Alvarez
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, 45435.,Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, 30322
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10
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Saywell SA, Ford TW, Kirkwood PA. Axonal projections of Renshaw cells in the thoracic spinal cord. Physiol Rep 2013; 1:e00161. [PMID: 24400162 PMCID: PMC3871475 DOI: 10.1002/phy2.161] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Revised: 10/17/2013] [Accepted: 10/18/2013] [Indexed: 02/01/2023] Open
Abstract
Renshaw cells are widely distributed in all segments of the spinal cord, but detailed morphological studies of these cells and their axonal branching patterns have only been made for lumbosacral segments. For these, a characteristic distribution of terminals was reported, including extensive collateralization within 1-2 mm of the soma, but then more restricted collaterals given off at intervals from the funicular axon. Previous authors have suggested that the projections close to the soma serve inhibition of motoneurons (known to be greatest for the motor nuclei providing the Renshaw cell excitation) but that the distant projections serve mainly the inhibition of other neurons. However, in thoracic segments, inhibition of motoneurons is known to occur over two to three segments (20-40 mm) from the presumed somatic locations of the Renshaw cells. Here, we report the first detailed morphological study of Renshaw cell axons outside the lumbosacral segments, which investigated whether this different distribution of motoneuron inhibition is reflected in a different pattern of Renshaw cell terminations. Four Renshaw cells in T7 or T8 segments were intracellularly labeled with neurobiotin in anesthetized cats and their axons traced for distances ≥6 mm from the somata. The only morphological difference detected within this distance in comparison with Renshaw cells in the lumbosacral cord was a minimal taper in the funicular axons, where in the lumbosacral cord this is pronounced. Patterns of termination were virtually identical to those in the lumbosacral segments, so we conclude that these patterns are unrelated to the pattern of motoneuronal inhibition.
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Affiliation(s)
- Shane A Saywell
- School of Health Sciences, Queen's Medical Centre, University of Nottingham Nottingham, NG7 2HA, U.K
| | - Timothy W Ford
- School of Health Sciences, Queen's Medical Centre, University of Nottingham Nottingham, NG7 2HA, U.K
| | - Peter A Kirkwood
- Sobell Department for Motor Neuroscience and Movement Disorders, UCL Institute of Neurology Queen Square, London, WC1N 3BG, U.K
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11
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Abstract
The concentration of transmitter in the synaptic cleft and its clearance time are one of the main determinants of synaptic strength. We estimated the time course of glycine at rat lumbar motoneurons synapses in spinal cord slices by recording synaptic currents in the presence of a low-affinity competitive antagonist at glycine receptors [2-(3-carboxypropyl)-3-amino-6-(4-methoxyphenyl)pyridazinium (SR-95531)]. Data were analyzed by using the established activation mechanism for glycine receptors and our measurements of SR-95531 binding rates. We show that this technique alone is not sufficient to determine simultaneously the peak concentration of transmitter and its clearance time. However, we found that block of the glial glycine transporter prolongs the glycine transient. This observation puts additional constraints on the range of possible values of the time course of glycine, indicating that glycine reaches a peak concentration of 2.2-3.5 mM and is cleared from the cleft with a time constant of 0.6-0.9 ms.
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12
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Elbasiouny SM, Mushahwar VK. Suppressing the excitability of spinal motoneurons by extracellularly applied electrical fields: insights from computer simulations. J Appl Physiol (1985) 2007; 103:1824-36. [PMID: 17702836 DOI: 10.1152/japplphysiol.00362.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effect of extracellularly applied electrical fields on neuronal excitability and firing behavior is attributed to the interaction between neuronal morphology and the spatial distribution and level of differential polarization induced by the applied field in different elements of the neuron. The presence of voltage-gated ion channels that mediate persistent inward currents (PICs) on the dendrites of spinal motoneurons enhances the influence of electrical fields on the motoneuronal firing behavior. The goal of the present study was to investigate, with a realistic motoneuron computer model, the effects of extracellularly applied electrical fields on the excitability of spinal motoneurons with the aim of reducing the increased motoneuronal excitability after spinal cord injury (SCI). Our results suggest that electrical fields could suppress the excitability of motoneurons and reduce their firing rate significantly by modulating the magnitude of their dendritic PIC. This effect was achieved at different field directions, intensities, and polarities. The reduction in motoneuronal firing rate resulted from the reduction in the magnitude of the dendritic PIC reaching the soma by the effect of the applied electrical field. This reduction in PIC was attributed to the dendritic field-induced differential polarization and the nonlinear current-voltage relationship of the dendritic PIC-mediating channels. Because of the location of the motoneuronal somata and initial segment with respect to the dendrites, these structures were minimally polarized by the applied field compared with the extended dendrites. In conclusion, electrical fields could be used for suppressing the hyperexcitability of spinal motoneurons after SCI and reducing the level of spasticity.
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Affiliation(s)
- Sherif M Elbasiouny
- Department of Biomedical Engineering , Univ. of Alberta, Edmonton, AB, Canada T6G 2S2
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13
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Abstract
Renshaw cell properties have been studied extensively for over 50 years, making them a uniquely well-defined class of spinal interneuron. Recent work has revealed novel ways to identify Renshaw cells in situ and this in turn has promoted a range of studies that have determined their ontogeny and organization of synaptic inputs in unprecedented detail. In this review we illustrate how mature Renshaw cell properties and connectivity arise through a combination of activity-dependent and genetically specified mechanisms. These new insights should aid the development of experimental strategies to manipulate Renshaw cells in spinal circuits and clarify their role in modulating motor output.
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Affiliation(s)
- Francisco J Alvarez
- Department of Neuroscience, Cell Biology & Physiology, Boonshoft School of Medicine, Wright State University, 3640 Col. Glenn Hwy, Dayton, OH 45435, USA.
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Zhang M, Møller M, Broman J, Sukiasyan N, Wienecke J, Hultborn H. Expression of calcium channel CaV1.3 in cat spinal cord: Light and electron microscopic immunohistochemical study. J Comp Neurol 2007; 507:1109-27. [DOI: 10.1002/cne.21595] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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15
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Anelli R, Heckman CJ. The calcium binding proteins calbindin, parvalbumin, and calretinin have specific patterns of expression in the gray matter of cat spinal cord. ACTA ACUST UNITED AC 2006; 34:369-85. [PMID: 16902759 DOI: 10.1007/s11068-006-8724-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2004] [Revised: 11/22/2004] [Accepted: 11/22/2004] [Indexed: 12/18/2022]
Abstract
Calcium binding proteins (CBPs) regulate intracellular levels of calcium (Ca(2+)) ions. CBPs are particularly interesting from a morphological standpoint, because they are differentially expressed in certain sub-populations of cells in the nervous system of various species of vertebrate animals. However, knowledge on the cellular regulation governing such cell-specific CBP expression is still incomplete. In this work on the L7 segment of the cat spinal cord, we analyzed the localization and morphology of neurons expressing the CBPs calbindin-28 KD (CB), parvalbumin (PV), and calretinin (CR), and co-expressing CB and PV, CB and CR, and PV and CR. Single CBP-positive ((+)) neurons showed specific distributions: (1) CB was present in small neurons localized in laminae I, II, III and X, in small to medium size neurons in laminae III-VI, and in medium to large neurons in laminae VI-VIII; (2) PV was present in small size neurons in laminae III and IV and in medial portions of laminae V and VI, medium neurons and in lamina X at the border with lamina VII, in medium to large neurons in laminae VII and VIII; (3) CR labeling was detected in small size neurons in laminae I, II, III and VIII, in medium to large size neurons in laminae I and III-VII, and in small to medium size neurons in lamina X. Double labeled neurons were a small minority of the CBP(+) cells. Co-expression of CB and PV was seen in 1 to 2% of the CBP(+) cells, and they were detected in the ventral and intermediate portions of lamina VII and in lamina X. Co-localization of CB and CR was present in 0.3% of the cells and these cells were localized in lamina II. Double labeling for PV and CR occurred in 6% of the cells, and the cells were localized in ventral part of lamina VII and in lamina VIII. Overall, these results revealed distinct and reproducible patterns of localization of the neurons expressing single CBPs and co-expressing two of them. Distinct differences of CBP expression between cat and other species are discussed. Possible relations between the cat L7 neurons expressing different CBPs with the neurons previously analyzed in cat and other animals are suggested.
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Affiliation(s)
- Roberta Anelli
- Department of Physiology, Northwestern Feinberg School of Medicine, Chicago, Illinois, USA.
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16
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Berkowitz A, Yosten GLC, Ballard RM. Somato-dendritic morphology predicts physiology for neurons that contribute to several kinds of limb movements. J Neurophysiol 2006; 95:2821-31. [PMID: 16452255 DOI: 10.1152/jn.01246.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It has been difficult to predict the behavioral roles of vertebrate CNS neurons based solely on their morphologies, especially for the neurons that control limb movements in adults. We examined the morphologies of spinal interneurons involved in limb movement control, using intracellular recording followed by Neurobiotin injection in the in vivo adult turtle spinal cord preparation. We report here the first description of a class of spinal interneurons whose somato-dendritic morphologies predict their robust activity during multiple forms of ipsilateral and contralateral fictive hindlimb scratching and fictive hindlimb withdrawal. These "transverse interneurons" or T cells have a mediolaterally elongated soma and a simple dendritic tree that is extensive in the transverse plane but restricted rostrocaudally. During fictive scratching, these cells display strong rhythmic modulation with higher peak firing rates than other scratch-activated interneurons. These higher peak firing rates are at least partly caused by T cells having larger phase-locked membrane potential oscillations and narrower action potentials with briefer afterhyperpolarizations than other scratch-activated interneurons. Many T cells have axon terminal arborizations in the ventral horn of the spinal cord hindlimb enlargement. Identification of this morphological and physiological class of spinal interneurons should facilitate further exploration of the mechanisms of hindlimb motor pattern selection and generation.
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Affiliation(s)
- Ari Berkowitz
- Department of Zoology, University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA.
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17
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Ishii K, Wong JK, Sumikawa K. Comparison of alpha2 nicotinic acetylcholine receptor subunit mRNA expression in the central nervous system of rats and mice. J Comp Neurol 2005; 493:241-60. [PMID: 16255031 PMCID: PMC4289636 DOI: 10.1002/cne.20762] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The nicotinic acetylcholine receptor (nAChR) alpha2 subunit was the first neuronal nAChR to be cloned. However, data for the distribution of alpha2 mRNA in the rodent exists in only a few studies. Therefore, we investigated the expression of alpha2 mRNA in the rat and mouse central nervous systems using nonradioactive in situ hybridization histochemistry. We detected strong hybridization signals in cell bodies located in the internal plexiform layer of the olfactory bulb, the interpeduncular nucleus of the midbrain, the ventral and dorsal tegmental nuclei, the median raphe nucleus of the pons, the ventral part of the medullary reticular nucleus, the ventral horn in the spinal cord of both rats and mice, and in a few Purkinje cells of rats, but not of mice. Cells that moderately express alpha2 mRNA were localized to the cerebral cortex layers V and VI, the subiculum, the oriens layer of CA1, the medial septum, the diagonal band complex, the substantia innominata, and the amygdala of both animals. They were also located in a few midbrain nuclei of rats, whereas in mice they were either few or absent in these areas. However, in the upper medulla oblongata alpha2 mRNA was expressed in several large neurons of the gigantocellular reticular nucleus and the raphe magnus nucleus of mice, but not of rats. The data obtained show that a similar pattern of alpha2 mRNA expression exists in both rats and mice, with the exception of a few regions, and provide the basis for cellular level analysis.
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Affiliation(s)
- Katsuyoshi Ishii
- Department of Neurobiology and Behavior, University of California, Irvine, 92697-4550, USA.
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18
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González-Forero D, Alvarez FJ. Differential postnatal maturation of GABAA, glycine receptor, and mixed synaptic currents in Renshaw cells and ventral spinal interneurons. J Neurosci 2005; 25:2010-23. [PMID: 15728841 PMCID: PMC6726047 DOI: 10.1523/jneurosci.2383-04.2005] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Renshaw cells (RCs) receive excitatory inputs from motoneurons to which then they inhibit. The gain of this spinal recurrent inhibitory circuit is modulated by inhibitory synapses on RCs. Inhibitory synapses on RCs mature postnatally, developing unusually large postsynaptic gephyrin clusters that colocalize glycine and GABA(A) receptors. We hypothesized that these features potentiate inhibitory currents in RCs. Thus, we analyzed glycinergic and GABAergic "inhibitory" miniature postsynaptic currents (mPSCs) in neonatal [postnatal day 1 (P1) to P5] and mature (P9-P15) RCs and compared them to other ventral interneurons (non-RCs). Recorded neurons were Neurobiotin filled and identified as RCs or non-RCs using post hoc immunohistochemical criteria. Glycinergic, GABAergic, and mixed glycine/GABA mPSCs matured differently in RCs and non-RCs. In RCs, glycinergic and GABA(A) mPSC peak amplitudes increased 230 and 45%, respectively, from P1-P5 to P9-P15, whereas in non-RCs, glycinergic peak amplitudes changed little and GABA(A) amplitudes decreased. GABA(A) mPSCs were slower in RCs (P1-P5, tau = 58 ms; P9-P15, tau = 43 ms) compared with non-RCs (P1-P5, tau = 27 ms; P9-P15, tau = 14 ms). Thus, fast glycinergic currents dominated "mixed" mPSC peak amplitudes in mature RCs, and GABA(A) currents dominated their long decays. In non-RCs, GABAergic and mixed events had shorter durations, and their frequencies decreased with development. Functional maturation of inhibitory synapses on RCs correlates well with increased glycine receptor recruitment to large gephyrin patches, colocalization with alpha3/alpha5-containing GABA(A) receptors, and maintenance of GABA/glycine corelease. As a result, charge transfer in GABA, glycine, or mixed mPSCs was larger in mature RCs than in non-RCs, suggesting RCs receive potent inhibitory synapses.
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Affiliation(s)
- David González-Forero
- Department of Anatomy and Physiology, Wright State University, Dayton, Ohio 45435, USA
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Nissen UV, Mochida H, Glover JC. Development of projection-specific interneurons and projection neurons in the embryonic mouse and rat spinal cord. J Comp Neurol 2005; 483:30-47. [PMID: 15672401 DOI: 10.1002/cne.20435] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Interneurons and projection neurons in the lumbar spinal cord of mouse and rat embryos were labeled retrogradely with fluorescent dextran amines from a distance of one segment from the segment of origin [lumbar segment (L) 2]. Six classes with specific axonal projections (ipsilateral ascending, descending, and bifurcating, and commissural ascending, descending, and bifurcating) were identified by differential labeling in both species and followed from embryonic day (E)12 to birth in the mouse. Neurons with shorter projections (intrasegmental interneurons) were not studied. We show that the four nonbifurcating neuron classes occupy characteristic, partially overlapping domains in the transverse plane, indicating a systematic pattern of migration and settlement related to axon trajectories. The number of neurons in each of the nonbifurcating classes increased steadily during development. Bifurcating neurons represented a minor fraction of the total throughout development and had relatively scattered positions within the ipsilateral and commissural neuron domains. Combination of retrograde tracing and immunohistochemistry for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) showed that none of the spinal neurons in the six projection-specific classes was GABA positive, suggesting that all GABA-positive spinal neurons, including previously described GABA-positive commissural neurons, are unlikely to have projections exceeding one or two segments in either direction.
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Affiliation(s)
- Ulla Vig Nissen
- Department of Physiology, Institute of Basic Medical Science, University of Oslo, 0317 Oslo, Norway
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20
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Berkowitz A. Propriospinal projections to the ventral horn of the rostral and caudal hindlimb enlargement in turtles. Brain Res 2004; 1014:164-76. [PMID: 15213001 DOI: 10.1016/j.brainres.2004.04.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/09/2004] [Indexed: 10/26/2022]
Abstract
In limbed vertebrates, the capacity to generate rhythmic motor patterns for locomotion and scratching is distributed over spinal cord segments of the limb enlargement (e.g., lumbosacral segments), but within this region, rostral segments are more rhythmogenic than caudal segments. The underlying reasons for this rostrocaudal asymmetry are not clear. One possibility is that rostral and caudal segments receive distinct sets of propriospinal projections. To test this hypothesis, I injected horseradish peroxidase (HRP) into the ventral horn unilaterally in a rostral or caudal segment of the turtle hindlimb enlargement. I quantitatively assessed the distributions of retrogradely labeled neurons in six hindlimb enlargement and pre-enlargement segments. The cross-sectional distribution did not depend on which segment was injected. Ipsilateral labeling occurred predominantly in the deep dorsal horn, the lateral part of the intermediate zone, and the dorsal two-thirds of the ventral horn, while contralateral labeling occurred mainly in the medial part of the ventral horn and the lateral part of the intermediate zone. This cross-sectional distribution is similar to what has been seen in mammals. The rostrocaudal distribution of labeled cells, however, depended on which segment was injected. Rostral injections gave rise to rostrally skewed distributions, dominated by descending propriospinal neurons. Caudal injections gave rise to caudally skewed distributions, dominated by ascending propriospinal neurons. Thus, rostral segments of the hindlimb enlargement received more propriospinal inputs from immediately rostral than immediately caudal segments, while the reverse was true for inputs to caudal segments. This anatomical asymmetry may contribute to known functional asymmetries within the enlargement.
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Affiliation(s)
- Ari Berkowitz
- Department of Zoology, University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA.
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21
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Bui TV, Cushing S, Dewey D, Fyffe RE, Rose PK. Comparison of the morphological and electrotonic properties of Renshaw cells, Ia inhibitory interneurons, and motoneurons in the cat. J Neurophysiol 2003; 90:2900-18. [PMID: 12878716 DOI: 10.1152/jn.00533.2003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The morphological and electrotonic properties of 4 motoneurons, 8 Ia inhibitory interneurons, and 4 Renshaw cells were compared. The morphological analysis, based on 3-D reconstructions of the cells, revealed that dendrites of motoneurons are longer and more extensively branched. Renshaw cells have dendrites that are shorter and simpler in structure. Dendrites of Ia inhibitory interneurons could be as long as those of motoneurons but the branching structure resembled that of Renshaw cells. Compartmental models were used to determine the electrotonic properties of the paths from each dendritic terminal to the soma. The attenuations of steady-state voltage changes in motoneurons were 3 and 7 times larger than in Ia inhibitory interneurons and Renshaw cells, respectively. The same relative order was observed for current attenuation and electrotonic length. The dendritic input resistances in Renshaw cells were 2 and 4 times larger than in Ia inhibitory interneurons and motoneurons, respectively. The difference in these electrotonic properties increased during higher synaptic activity as modeled by a decrease of Rm. The peak amplitudes of voltage transients at sites of brief, synaptic-like changes in conductance were highly dependent on cell class and were largest in Renshaw cells and smallest in motoneurons. In combination with class-specific differences in the attenuation of transient voltage signals, this led to large differences in the peak amplitudes of somatic voltage transients. Differences in the rise times and half-widths of the voltage transients were observed as well. Thus, based on passive properties, each cell class has a unique set of input/output properties.
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Affiliation(s)
- T V Bui
- Canadian Institutes of Health Research Group in Sensory-Motor Systems, Department of Physiology, Queen's University, Kingston K7L 3N6, Canada.
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22
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Dourado M, Sargent PB. Properties of nicotinic receptors underlying Renshaw cell excitation by alpha-motor neurons in neonatal rat spinal cord. J Neurophysiol 2002; 87:3117-25. [PMID: 12037212 DOI: 10.1152/jn.2002.87.6.3117] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We used anatomical and physiological approaches to characterize nicotinic receptors (AChRs) on Renshaw cells of the neonatal rat spinal cord. Confocal imaging of Renshaw cells, identified by their characteristic pattern of gephyrin immunoreactivity, revealed that these neurons are immuno-positive for the alpha4 and beta2 AChR subunits but not for the alpha7 subunit. We used whole cell recording in spinal cord slices to characterize synaptic transmission from alpha-motor neurons to Renshaw cells, which could be identified pharmacologically by the sensitivity of transmission to d-tubocurarine. alpha-Motor neuron-to-Renshaw cell synapses were blocked by 10 microM dihydro-beta-erythroidine (dHbetaE), but not 50 nM methyllycaconitine (MLA), a selective alpha7 antagonist. These findings support a role for alpha4beta2-like AChRs, but not alpha7 AChRs, in rapid excitatory transmission between alpha-motor neurons and Renshaw cells in rat spinal cord.
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Affiliation(s)
- Michelle Dourado
- Departments of Stomatology and Physiology, University of California, San Francisco, California 94143, USA
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23
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Abstract
The ability to perform stepping and standing can be reacquired after complete thoracic spinal cord transection in adult cats with appropriate, repetitive training. We now compare GAD(67)A levels in the spinal cord of cats that were trained to step or stand. We confirmed that a complete spinal cord transection at approximately T12 increases glutamic acid decarboxylase (GAD)(67) in both the dorsal and ventral horns of L5-L7. We now show that step training decreases these levels toward control. Kinematic analyses show that this downward modulation is correlated inversely with stepping ability. Compared with intact cats, spinal cord-transected cats had increased punctate GAD(67) immunoreactivity around neurons in lamina IX at cord segments L5-L7. Compared with spinal nontrained cats, those trained to stand on both hindlimbs had more GAD(67) puncta bilaterally in a subset of lamina IX neurons. In cats trained to stand unilaterally, this elevated staining pattern was limited to the trained side and extended for at least 4 mm in the L6 and L7 segments. The location of this asymmetric GAD(67) staining corresponded to the motor columns of primary knee flexors, which are minimally active during standing, perhaps because of extensor-activated inhibitory interneuron projections. The responsiveness to only a few days of motor training, as well as the GABA-synthesizing potential in the spinal cord, persists for at least 25 months after the spinal cord injury. This modulation is specific to the motor task that is performed repetitively and is closely linked to the ability of the animal to perform a specific motor task.
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24
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Carr PA, Liu M, Zaruba RA. Enzyme histochemical profile of immunohistochemically identified Renshaw cells in rat lumbar spinal cord. Brain Res Bull 2001; 54:669-74. [PMID: 11403994 DOI: 10.1016/s0361-9230(01)00479-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Activity levels of cytochrome oxidase, acid phosphatase, and NADPH diaphorase were examined in the perikarya of immunohistochemically identified Renshaw cells from sections of rat lumbar spinal cord. Renshaw cell profiles were identified on the basis of their characteristic anti-gephyrin-immunofluorescent labelling. Intrasomatic densities of enzyme histochemical reaction product were employed as indicators of relative mitochondrial activity (cytochrome oxidase), intracytoplasmic digestion (acid phosphatase), or putative nitrergic signalling (NAPDH-diaphorase). Approximately half of the Renshaw cell somata examined displayed moderate levels of cytochrome oxidase reaction product (142 of 262 Renshaw cells) or low levels of acid phosphatase activity (156 of 243 Renshaw cells). A majority (160 of 202 cells) of Renshaw cells contained low intrasomatic levels of NADPH-diaphorase activity but most of these cells were closely apposed by at least one NADPH-diaphorase reactive axonal varicosity. Our findings suggest that moderate levels of perikaryal oxidative metabolism and low levels of intracytoplasmic digestion are sufficient for, and support, the unique physiological capabilities of Renshaw cells. The presence of NADPH-diaphorase containing somatic close contacts indicate that nitric oxide may have at least a minor role in the regulation of Renshaw cell activity. These results are complementary and consistent with previous morphological and pharmacological demonstrations of Renshaw cell heterogeneity.
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Affiliation(s)
- P A Carr
- Department of Anatomy and Cell Biology, University of North Dakota, Grand Forks, ND 58202, USA.
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25
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Abstract
Adult mammalian Renshaw cells express large and complex postsynaptic gephyrin/glycine receptor clusters on their surface. Larger gephyrin clusters correlate with more "efficacious" inhibitory synapses, in terms of larger postsynaptic quantal size amplitudes, in part because they likely contain more postsynaptic receptors (Lim et al. [1999] J. Physiol. (Lond.) 516:505-512; Oleskevich et al. [1999] J. Neurophysiology 82:312-319). Here, we studied the postnatal development of the gephyrin/glycine receptor cluster size on Renshaw cells. Renshaw cells were identified by their calbindin immunoreactivity, location and morphology, and presence of cholinergic input. The populations of clusters over developing Renshaw cells immunoreactive to gephyrin or glycine receptor alpha1 subunits were comparable in number, size, and complexity and displayed a high degree of colocalization (>90%) at all ages. Quantitative morphologic analysis was performed on gephyrin-immunoreactive clusters. In neonatal animals, Renshaw cells expressed small punctate gephyrin-immunoreactive clusters (mean cluster size +/- SD = 0.19 +/- 0.19 microm(2)at 2 days; 0.22 +/- 0. 19 microm(2)at 5 days). By 10 and 15 days of age, Renshaw cells exhibited gephyrin-immunoreactive clusters that were larger and more complex (0.32 +/- 0.19 microm(2) at 10 days; 0.41 +/- 0.32 microm(2) at 15 days). Cluster growth reached a plateau in 25- and 60-day-old Renshaw cells (0.45 +/- 0.43 microm(2); 0.56 +/- 0.55 microm(2), respectively). By using electron microscopy, we confirmed that gephyrin-immunoreactive clusters were located at postsynaptic sites at both early and late postnatal ages on Renshaw cells. The potential significance of this gephyrin/glycine receptor cluster size maturation that sets Renshaw cells apart from other interneurons is discussed.
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Affiliation(s)
- E J Geiman
- Department of Anatomy, Wright State University, Dayton, Ohio 45435, USA
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26
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Clowry GJ, Arnott GA, Clement-Jones M, Fallah Z, Gould S, Wright C. Changing pattern of expression of parvalbumin immunoreactivity during human fetal spinal cord development. J Comp Neurol 2000. [DOI: 10.1002/1096-9861(20000807)423:4<727::aid-cne14>3.0.co;2-q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Oleskevich S, Alvarez FJ, Walmsley B. Glycinergic miniature synaptic currents and receptor cluster sizes differ between spinal cord interneurons. J Neurophysiol 1999; 82:312-9. [PMID: 10400960 DOI: 10.1152/jn.1999.82.1.312] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The structural features of a synaptic connection between central neurons play an important role in determining the strength of the connection. In the present study, we have examined the relationship between the structural and functional properties of glycinergic synapses in the rat spinal cord. We have analyzed the structure of glycinergic receptor clusters on rat ventral horn interneurons using antibodies against the glycine receptor clustering protein, gephyrin. We have examined the properties of quantal glycinergic currents generated at these synapses using whole cell patch-clamp recordings of miniature postsynaptic inhibitory currents (mIPSCs) in rat spinal cord slices in vitro. Our immunolabeling results demonstrate that there is a considerable variability in the size of glycine receptor clusters within individual neurons. Furthermore there are large differences in the mean cluster size between neurons. These observations are paralleled closely by recordings of glycinergic mIPSCs. The mIPSC amplitude varies significantly within and between neurons. Results obtained using combined immunolabeling and electrophysiological recording on the same neurons show that cells with small glycine receptor clusters concurrently exhibit small mIPSCs. Our results suggest that the differences in the size of glycinergic receptor clusters may constitute an important factor contributing to the observed differences in mIPSC amplitude among spinal cord interneurons.
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Affiliation(s)
- S Oleskevich
- The Synaptic Structure and Function Group, Division of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT 0200, Australia
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28
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Carr PA, Pearson JC, Fyffe RE. Distribution of 5-hydroxytryptamine-immunoreactive boutons on immunohistochemically-identified Renshaw cells in cat and rat lumbar spinal cord. Brain Res 1999; 823:198-201. [PMID: 10095027 DOI: 10.1016/s0006-8993(98)01210-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A combination of anti-gephyrin- and anti-calbindin D28k-immunoreactivity was used to identify 129 and 171 Renshaw cells and their dendrites in cat and rat lumbar spinal cord, respectively. Using anti-5-hydroxytryptamine-immunoreactivity to label serotoninergic fibers and boutons, 1048 serotoninergic boutons were observed in close contact with the immunolabeled Renshaw cells, with an average of 4.4 and 2.8 close contacts on cat and rat Renshaw cells, respectively. Two-thirds of the observed appositions were formed on the somatic membrane.
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Affiliation(s)
- P A Carr
- Department of Anatomy, Wright State University, P.O. Box 927, Dayton, OH 45435, USA
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29
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Alvarez FJ, Dewey DE, McMillin P, Fyffe RE. Distribution of cholinergic contacts on Renshaw cells in the rat spinal cord: a light microscopic study. J Physiol 1999; 515 ( Pt 3):787-97. [PMID: 10066905 PMCID: PMC2269191 DOI: 10.1111/j.1469-7793.1999.787ab.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
1. Cholinergic terminals in the rat spinal cord were revealed by immunohistochemical detection of the vesicular acetycholine transporter (VAChT). In order to determine the relationships of these terminals to Renshaw cells, we used dual immunolabelling with antibodies against gephyrin or calbindin D28k to provide immunohistochemical identification of Renshaw cells in lamina VII of the ventral horn. 2. A total of 50 Renshaw cells were analysed quantitatively using a computer-aided reconstruction system to provide accurate localization of contact sites and determination of somatic and dendritic surface area. Dendrites could be traced for up to 413 microm from the soma in calbindin D28k-identified Renshaw cells and up to 184 microm in gephyrin-identified cells. 3. A total of 3330 cholinergic terminals were observed on 50 Renshaw cells, with a range of 21-138 terminal appositions per cell (mean 66.6 +/- 25.56 contacts per cell). The vast majority (83.5 %) of the terminals were apposed to dendrites rather than the soma. The overall density of cholinergic contacts increased from a little above 1 per 100 microm2 on the soma and initial 25 microm of proximal dendrites to 4-5 per 100 microm2 on the surface of dendritic segments located 50-250 microm from the soma. Single presynaptic fibres frequently formed multiple contacts with the soma and/or dendrites of individual Renshaw cells. 4. VAChT-immunoreactive terminals apposed to Renshaw cells varied in size from 0.6 to 6.9 microm in diameter (mean 2.26 +/- 0.94; n = 986) and were on average smaller than the cholinergic C-terminals apposed to motoneurones, but larger than VAChT-immunoreactive terminals contacting other ventral horn interneurones. 5. The high density and relatively large size of many cholinergic terminals on Renshaw cells presumably correlates with the strong synaptic connection between motoneurones and Renshaw cells. The fact that the majority of contacts are distributed over the dendrites makes the motoneurone axon collateral input susceptible to inhibition by the prominent glycinergic inhibitory synapses located on the soma and proximal dendrites. The relative positions and structural features of the excitatory cholinergic and inhibitory glycinergic synapses may explain why Renshaw cells, although capable of firing at very high frequency following motor axon stimulation, appear to fire at relatively low rates during locomotor activity.
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Affiliation(s)
- F J Alvarez
- Department of Anatomy, Wright State University, Dayton, OH 45435, USA
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30
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Fallah Z, Clowry GJ. The effect of a peripheral nerve lesion on calbindin D28k immunoreactivity in the cervical ventral horn of developing and adult rats. Exp Neurol 1999; 156:111-20. [PMID: 10192782 DOI: 10.1006/exnr.1999.7017] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Expression of calbindin D28k (CB) immunoreactivity by putative Renshaw cells is substantially downregulated by sciatic motoneuron axotomy in the adult rat. The present study investigated the effect of median and ulnar nerve lesion at different ages on ventral horn CB immunoreactivity 7 days after the injury to see whether similar results were obtained in the cervical cord and during development. Two major differences were observed. First, axotomy induced CB immunoreactivity in some motoneurons, confirmed by retrograde labeling of the injured neurons with fast blue (FB). Observation of fluorescent phagocytic microglia revealed that some motoneuron death occurred following lesions at postnatal day 2 (P2) and P7, but not at P21 or P63. A significantly higher proportion of remaining FB labeled motoneurons expressed CB following lesion at P2 (mean 33% +/- 7.6 SD) and P7 (30.6% +/- 5.2) than at P28 (14.0% +/- 1.9). Second, CB expression by putative Renshaw cells was not significantly downregulated ipsilateral to the lesion. CB immunofluorescent putative Renshaw cells were counted in sections containing FB labeled motoneurons. No consistent differences in the numbers of Renshaw cells ipsilateral and contralateral to the lesion were found at any age. To confirm that these neurons really were Renshaw cells, the mediators of recurrent inhibition to cholinergic motoneurons, we employed double-immunofluorescence labeling with confocal microscopy. The group of CB immunopositive neurons located among the converging ventral roots in the cervical cord were closely apposed by many axon terminals immunoreactive for (i) vesicular acetylcholine transporter and (ii) cholera toxin B localized to motor axon collaterals by injection of this tracer into a distal forelimb muscle. We conclude that motoneuron axotomy need not always downregulate CB expression in associated Renshaw cells. In addition, some brachial motoneurons respond to axotomy by expressing CB.
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Affiliation(s)
- Z Fallah
- Department of Child Health, Newcastle University, Newcastle upon Tyne, NE1 4LP, United Kingdom
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Carr PA, Alvarez FJ, Leman EA, Fyffe RE. Calbindin D28k expression in immunohistochemically identified Renshaw cells. Neuroreport 1998; 9:2657-61. [PMID: 9721951 DOI: 10.1097/00001756-199808030-00043] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Double immunofluorescence was utilized to determine whether Renshaw cells contain calbindin D28k immunoreactivity. Renshaw cells were identified by their characteristic expression patterns of gephyrin immunoreactivity in sections of rat and cat lumbar spinal cord. In the rat, all neurons classified as Renshaw cells (n = 487) also contained calbindin D28k-immunoreactivity, and all calbindin D28k-immunoreactive cells located in the ventral-most region of lamina VII expressed the characteristic gephyrin labeling and morphology of Renshaw cells. In the cat, fewer than half of the Renshaw cells (47%; n = 128) were double-labeled. In both species, occasional calbindin D28k-immunoreactive Renshaw cells were identified within motor nuclei in lamina IX. The distinctive immunolabeling of Renshaw cells allowed us to estimate that there are about 250 Renshaw cells in each ventral horn of the fourth lumbar segment of rat spinal cord, and about 750 cells per ventral horn in the L6 segment of the cat. We conclude that the functional properties of Renshaw cells, including their ability to fire action potentials at high rates, likely require specific homeostatic mechanisms including strong intracellular calcium buffering, the precise mechanisms of which may vary between species.
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Affiliation(s)
- P A Carr
- Department of Anatomy, Wright State University, Dayton, OH 45435, USA
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Abstract
This article reviews presumed roles of recurrent inhibition in motor control, that have been proposed over the past five decades. The discussion is structured in an order of increasing complexity. It starts out with the simplest and earliest circuit, that is recurrent self-inhibition of skeleto-motoneurons, and related functions. It soon becomes clear that in order to understand recurrent inhibition, we must look beyond the simple self-inhibitory CNS circuit. First, recurrent inhibition must be seen in the context of other neural circuits. Second, some quantitative features appear to be correlated with features of the neuromusculo-skeletal periphery. Third, the aspect of lateral inhibition between different members of a motoneuron pool as well as between different motoneuron pools points to the essential multiple input-multiple output structure of recurrent inhibition that again can be understood only by correlating it with features of the neuromusculo-skeletal periphery. Another extension results from the discovery that recurrent inhibition affects not only skeleto-motoneurons, but also gamma-motoneurons, Ia inhibitory interneurons mediating reciprocal inhibition between antagonist motoneurons, other Renshaw cells and cells of origin of the ventral spinocerebellar tract (VSCT). Then the view broadens again, investigating the potential role that recurrent inhibition plays in two far-ranging theories of motor control, the inverse-dynamics approach and the equilibrium-point hypothesis. Finally, the present author tries to formulate, in broad strokes, a personal functional interpretation of recurrent inhibition. All the functional considerations, right or wrong, should yield ideas for new experiments, and this then is the last objective of this review.
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Affiliation(s)
- U Windhorst
- Department of Clinical Neurosciences, University of Calgary, Faculty of Medicine, Alberta, Canada.
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O'Hanlon GM, Lowrie MB. Evidence for age-dependent changes in motoneuron dendritic morphology following neonatal nerve-crush in the rat. Neuroscience 1993; 57:995-1005. [PMID: 8309557 DOI: 10.1016/0306-4522(93)90044-g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Motoneurons supplying the extensor hallucis longus muscle of the rat were temporarily separated from the muscle by sciatic nerve-crush at five days postnatally. Such treatment permanently alters the reflex response of the affected motoneurons without the large-scale cell death associated with nerve-crush at birth. After reinnervation, the motoneurons were retrogradely labelled with cholera toxin subunit-B conjugated to horseradish peroxidase and the dendritic tree of each labelled cell was analysed. When compared to normal data, significantly higher levels of dendritic density were observed in the rostrodorsally orientated parts of the dendritic field. This was similar to that found previously for the same motor pool after nerve-crush at birth. However, in other parts of the field where a lower dendritic density was found after nerve-crush at birth, no change was seen after nerve-crush at five days. These data present evidence for the influence of sensory afferents on the development of motoneuron dendrites. Taken together with the previous findings after nerve-crush at birth, we suggest that the differential dendritic changes caused by neonatal nerve lesion contribute to an imbalance in the pattern of excitatory and inhibitory inputs to the motoneuron, which results either in cell death, or the abnormal activity seen in those motoneurons which survive.
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Affiliation(s)
- G M O'Hanlon
- Department of Anatomy and Cell Biology, Saint Mary's Hospital Medical School, Imperial College, London, U.K
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Sanna PP, Celio MR, Bloom FE, Rende M. Presumptive Renshaw cells contain decreased calbindin during recovery from sciatic nerve lesions. Proc Natl Acad Sci U S A 1993; 90:3048-52. [PMID: 8464922 PMCID: PMC46234 DOI: 10.1073/pnas.90.7.3048] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
A subpopulation of calbindin-immunoreactive neurons in lamina VII of the spinal cord has been identified by its location as Renshaw cells, the anatomical substrate for recurrent inhibition. The expression of calbindin (28 kDa) in these calbindin-containing rat ventral horn interneurons was studied with immunocytochemistry after sciatic nerve injuries. One week after axotomy calbindin immunoreactivity was strongly reduced on the lesioned side between levels L4 and L6, while calbindin-containing neurons and fibers were still numerous contralaterally and cranially to the lesioned levels. With the progression of regeneration, calbindin-immunoreactive neurons reappeared, reaching a normal distribution 6-8 weeks after the crush. Similar changes could be mimicked by the intramuscular administration of botulinum toxin. These results suggest that calbindin expression in putative Renshaw cells of the spinal cord might be functionally responsive and that maintenance of calbindin expression may depend on the integrity of motoneurons and neuromuscular transmission.
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Affiliation(s)
- P P Sanna
- Department of Neuropharmacology, Scripps Research Institute, La Jolla, CA 92037
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Abstract
To identify spinal neurons that may synthesize nitric oxide, cells and fibers histochemically stained for NADPH diaphorase (a nitric oxide synthase) were studied in the spinal cord of rats. The histochemical reaction gave an image similar to the best Golgi impregnations, staining cells down to their finest processes. Transverse, horizontal, and parasagittal 50 and 100 microns sections were used to follow dendritic and axonal arborizations of stained neurons. Major cell groups were identified in the superficial dorsal horn and around the central canal (at all spinal levels), and in the intermediolateral cell column (at thoracic and sacral levels). Scattered positive cells were also found in deeper dorsal horn, ventral horn, and white matter. In some cases, axons of cells in the dorsal horn could be traced into the white matter; many of these cells resembled neurons projecting to various supraspinal targets. Stained cells in the intermediolateral column, which sent their axons into the ventral root, were presumed to be preganglionic autonomic neurons. Dense plexes of fibers were stained in laminae I and II and in the intermediolateral column. A large number of NADPH diaphorase-positive neurons in the spinal cord appear to be involved in visceral regulation. Fibers of the intermediolateral system had a special relationship with vasculature, suggesting that nitric oxide may help to couple neural activity with regional blood flow in the spinal cord. The abundance of NADPH diaphorase-positive neurons and fibers in the superficial dorsal horn suggests that nitric oxide may also be involved in spinal sensory processing.
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Affiliation(s)
- J G Valtschanoff
- Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill 27599
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Fyffe RE. Glycine-like immunoreactivity in synaptic boutons of identified inhibitory interneurons in the mammalian spinal cord. Brain Res 1991; 547:175-9. [PMID: 1860070 DOI: 10.1016/0006-8993(91)90590-r] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Glycine is thought to be a major inhibitory neurotransmitter in the mammalian CNS. Two types of physiologically identified interneurons, Renshaw cells and Ia inhibitory interneurons, were intracellularly stained with horseradish peroxidase, and their axon terminals were studied at the electron microscopic level. Post-embedding immunogold procedures were used to reveal the presence of glycine-like immunoreactivity. The synaptic terminals of both types of interneuron were significantly enriched with glycine-like immunoreactivity, providing support for the idea that glycine is a mediator of synaptic transmission in the recurrent and reciprocal inhibitory pathways to motoneurons.
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Affiliation(s)
- R E Fyffe
- Department of Physiology, University of North Carolina, Chapel Hill 27599-7545
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