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Heinzel JC, Oberhauser V, Keibl C, Swiadek N, Längle G, Frick H, Kolbenschlag J, Prahm C, Grillari J, Hercher D. Evaluation of Functional Recovery in Rats After Median Nerve Resection and Autograft Repair Using Computerized Gait Analysis. Front Neurosci 2021; 14:593545. [PMID: 33551723 PMCID: PMC7859340 DOI: 10.3389/fnins.2020.593545] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 12/11/2020] [Indexed: 12/12/2022] Open
Abstract
Computerized gait analysis is a common evaluation method in rat models of hind limb nerve injuries, but its use remains unpublished in models of segmental nerve injury of the forelimb. It was the aim of this work to investigate if computerized gait analysis is a feasible evaluation method in a rat model of segmental median nerve injury and autograft repair. Ten male Lewis rats underwent 7-mm resection of the right median nerve with immediate autograft repair. The left median nerve was resected without repair and served as an internal control. Animals were assessed for 12 weeks after surgery via CatWalk (CW) gait analysis every 2 weeks. Evaluation of motor recovery by means of the grasping test was performed weekly while electrophysiological measurements were performed at the end of the observation period. CW data were correlated with grasping strength at each post-operative time point. CW data were also correlated with electrophysiology using linear regression analysis. Principal component analysis was performed to identify clusters of outcome metrics. Recovery of motor function was observable 4 weeks after surgery, but grasping strength was significantly reduced (p < 0.01) compared to baseline values until post-operative week 6. In terms of sensory recovery, the pain-related parameter Duty Cycle showed significant (p < 0.05) recovery starting from post-operative week 8. The Print Area of the right paw was significantly (p < 0.05) increased compared to the left side starting from post-operative week 10. Various parameters of gait correlated significantly (p < 0.05) with mean and maximum grasping strength. However, only Stand Index showed a significant correlation with compound muscle action potential (CMAP) amplitude (p < 0.05). With this work, we prove that computerized gait analysis is a valid and feasible method to evaluate functional recovery after autograft repair of the rat median nerve. We were able to identify parameters such as Print Area, Duty Cycle, and Stand Index, which allow assessment of nerve regeneration. The course of these parameters following nerve resection without repair was also assessed. Additionally, external paw rotation was identified as a valid parameter to evaluate motor reinnervation. In summary, computerized gait analysis is a valuable additional tool to study nerve regeneration in rats with median nerve injury.
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Affiliation(s)
- Johannes C Heinzel
- Department of Hand, Plastic, Reconstructive and Burn Surgery, BG Trauma Center Tuebingen, Eberhard Karls University Tuebingen, Tuebingen, Germany.,Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Viola Oberhauser
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Claudia Keibl
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Nicole Swiadek
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Gregor Längle
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Helen Frick
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Jonas Kolbenschlag
- Department of Hand, Plastic, Reconstructive and Burn Surgery, BG Trauma Center Tuebingen, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Cosima Prahm
- Department of Hand, Plastic, Reconstructive and Burn Surgery, BG Trauma Center Tuebingen, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Johannes Grillari
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria.,Department of Biotechnology, Institute of Molecular Biotechnology, BOKU-University of Natural Resources and Life Sciences Vienna, Vienna, Austria
| | - David Hercher
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
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Heinzel J, Längle G, Oberhauser V, Hausner T, Kolbenschlag J, Prahm C, Grillari J, Hercher D. Use of the CatWalk gait analysis system to assess functional recovery in rodent models of peripheral nerve injury – a systematic review. J Neurosci Methods 2020; 345:108889. [DOI: 10.1016/j.jneumeth.2020.108889] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/28/2020] [Accepted: 07/28/2020] [Indexed: 02/07/2023]
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Heinzel JC, Hercher D, Redl H. The course of recovery of locomotor function over a 10-week observation period in a rat model of femoral nerve resection and autograft repair. Brain Behav 2020; 10:e01580. [PMID: 32097542 PMCID: PMC7177579 DOI: 10.1002/brb3.1580] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 12/26/2019] [Accepted: 01/30/2020] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND A great extent of knowledge on peripheral nerve regeneration has been gathered using the rat sciatic nerve model. The femoral nerve model of the rat offers an interesting alternative, as it lacks disadvantageous features such as automutilation. For the analysis of locomotor behavior in rats after sciatic nerve injury, the CatWalk™ XT Gait Analysis System is often used. However, lesions of the femoral nerve in the rat have yet remained unstudied with this method. MATERIAL AND METHODS Ten male Sprague Dawley rats were evaluated with the CatWalk XT to study their gait after a 6-mm resection of the right femoral nerve and reconstruction with an autologous nerve graft. Animals were observed for 10 weeks after surgery. RESULTS Print Area, Print Length, Swing Speed, and Duty Cycle decreased to a minimum of 40% of baseline 2 weeks after surgery. Swing Time was elevated more than twofold at this time point. However, all these parameters recovered back to >90% of baseline values at 10 weeks after surgery. This degree of functional recovery has not been reported after sciatic nerve resection and autograft repair. Base of support varied minimally postoperatively in contrast to a strong decrement after sciatic nerve resection and repair. CONCLUSION We hereby provide a comprehensive in-depth analysis of how to study functional recovery after injury of the femoral nerve in the rat via the CatWalk XT. We place special emphasis on highlighting the differences between the femoral nerve and sciatic nerve injury model in this context.
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Affiliation(s)
- Johannes Christoph Heinzel
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology in the AUVA Trauma Research Center, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - David Hercher
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology in the AUVA Trauma Research Center, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Heinz Redl
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology in the AUVA Trauma Research Center, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria
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4
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Zurawski Z, Thompson Gray AD, Brady LJ, Page B, Church E, Harris NA, Dohn MR, Yim YY, Hyde K, Mortlock DP, Jones CK, Winder DG, Alford S, Hamm HE. Disabling the Gβγ-SNARE interaction disrupts GPCR-mediated presynaptic inhibition, leading to physiological and behavioral phenotypes. Sci Signal 2019; 12:12/569/eaat8595. [PMID: 30783011 DOI: 10.1126/scisignal.aat8595] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
G protein-coupled receptors (GPCRs) that couple to Gi/o proteins modulate neurotransmission presynaptically by inhibiting exocytosis. Release of Gβγ subunits from activated G proteins decreases the activity of voltage-gated Ca2+ channels (VGCCs), decreasing excitability. A less understood Gβγ-mediated mechanism downstream of Ca2+ entry is the binding of Gβγ to SNARE complexes, which facilitate the fusion of vesicles with the cell plasma membrane in exocytosis. Here, we generated mice expressing a form of the SNARE protein SNAP25 with premature truncation of the C terminus and that were therefore partially deficient in this interaction. SNAP25Δ3 homozygote mice exhibited normal presynaptic inhibition by GABAB receptors, which inhibit VGCCs, but defective presynaptic inhibition by receptors that work directly on the SNARE complex, such as 5-hydroxytryptamine (serotonin) 5-HT1b receptors and adrenergic α2a receptors. Simultaneously stimulating receptors that act through both mechanisms showed synergistic inhibitory effects. SNAP25Δ3 homozygote mice had various behavioral phenotypes, including increased stress-induced hyperthermia, defective spatial learning, impaired gait, and supraspinal nociception. These data suggest that the inhibition of exocytosis by Gi/o-coupled GPCRs through the Gβγ-SNARE interaction is a crucial component of numerous physiological and behavioral processes.
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Affiliation(s)
- Zack Zurawski
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612, USA
| | | | - Lillian J Brady
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - Brian Page
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Emily Church
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Nicholas A Harris
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Michael R Dohn
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - Yun Young Yim
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - Karren Hyde
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - Douglas P Mortlock
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Carrie K Jones
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA
| | - Danny G Winder
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Simon Alford
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Heidi E Hamm
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, 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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6
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Anglister L, Cherniak M, Lev-Tov A. Ascending pathways that mediate cholinergic modulation of lumbar motor activity. J Neurochem 2017; 142 Suppl 2:82-89. [PMID: 28791705 DOI: 10.1111/jnc.14065] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 05/01/2017] [Accepted: 05/03/2017] [Indexed: 01/10/2023]
Abstract
Deciphering neuronal pathways that reactivate spinal central pattern generators (CPGs) and modulate the activity of spinal motoneurons in mammals in the absence of supraspinal control is important for understanding of neural control of movement and for developing novel therapeutic approaches to improve the mobility of spinal cord injury patients. Previously, we showed that the sacral and lumbar cholinergic system could potently modulate the locomotor CPGs in newborn rodents. Here, we review these and our more recent studies of sacral relay neurons with lumbar projections to the locomotor CPGs and to lumbar motoneurons and demonstrate that sacral and lumbar cholinergic components have the capacity to control the frequency of the locomotor CPGs and at the same time the motor output of the activated lumbar motoneurons during motor behavior. A model describing the suggested ascending sacro-lumbar connectivity involved in modulation of the locomotor rhythm by sacral cholinergic components is proposed and discussed. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.
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Affiliation(s)
- Lili Anglister
- Department of Medical Neurobiology, IMRIC, the Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Meir Cherniak
- Department of Medical Neurobiology, IMRIC, the Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Aharon Lev-Tov
- Department of Medical Neurobiology, IMRIC, the Hebrew University-Hadassah Medical School, Jerusalem, Israel
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7
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Kusakabe TG. Identifying Vertebrate Brain Prototypes in Deuterostomes. DIVERSITY AND COMMONALITY IN ANIMALS 2017. [DOI: 10.1007/978-4-431-56469-0_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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8
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Shaping the Output of Lumbar Flexor Motoneurons by Sacral Neuronal Networks. J Neurosci 2016; 37:1294-1311. [PMID: 28025254 DOI: 10.1523/jneurosci.2213-16.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 12/11/2016] [Accepted: 12/14/2016] [Indexed: 12/27/2022] Open
Abstract
The ability to improve motor function in spinal cord injury patients by reactivating spinal central pattern generators (CPGs) requires the elucidation of neurons and pathways involved in activation and modulation of spinal networks in accessible experimental models. Previously we reported on adrenoceptor-dependent sacral control of lumbar flexor motoneuron firing in newborn rats. The current work focuses on clarification of the circuitry and connectivity involved in this unique modulation and its potential use. Using surgical manipulations of the spinal gray and white matter, electrophysiological recordings, and confocal microscopy mapping, we found that methoxamine (METH) activation of sacral networks within the ventral aspect of S2 segments was sufficient to produce alternating rhythmic bursting (0.15-1 Hz) in lumbar flexor motoneurons. This lumbar rhythm depended on continuity of the ventral funiculus (VF) along the S2-L2 segments. Interrupting the VF abolished the rhythm and replaced it by slow unstable bursting. Calcium imaging of S1-S2 neurons, back-labeled via the VF, revealed that ∼40% responded to METH, mostly by rhythmic firing. All uncrossed projecting METH responders and ∼70% of crossed projecting METH responders fired with the concurrent ipsilateral motor output, while the rest (∼30%) fired with the contralateral motor output. We suggest that METH-activated sacral CPGs excite ventral clusters of sacral VF neurons to deliver the ascending drive required for direct rhythmic activation of lumbar flexor motoneurons. The capacity of noradrenergic-activated sacral CPGs to modulate the activity of lumbar networks via sacral VF neurons provides a novel way to recruit rostral lumbar motoneurons and modulate the output required to execute various motor behaviors. SIGNIFICANCE STATEMENT Spinal central pattern generators (CPGs) produce the rhythmic output required for coordinating stepping and stabilizing the body axis during movements. Electrical stimulation and exogenous drugs can reactivate the spinal CPGs and improve the motor function in the absence of descending supraspinal control. Since the body-stabilizing sacral networks can activate and modulate the limb-moving lumbar circuitry, it is important to clarify the functional organization of sacral and lumbar networks and their linking pathways. Here we decipher the ascending circuitry linking adrenoceptor-activated sacral CPGs and lumbar flexor motoneurons, thereby providing novel insights into mechanisms by which sacral circuitry recruits lumbar flexors, and enhances the motor output during lumbar afferent-induced locomotor rhythms. Moreover, our findings might help to improve drug/electrical stimulation-based therapy to accelerate locomotor-based rehabilitation.
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Daghfous G, Green WW, Alford ST, Zielinski BS, Dubuc R. Sensory Activation of Command Cells for Locomotion and Modulatory Mechanisms: Lessons from Lampreys. Front Neural Circuits 2016; 10:18. [PMID: 27047342 PMCID: PMC4801879 DOI: 10.3389/fncir.2016.00018] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 03/07/2016] [Indexed: 11/13/2022] Open
Abstract
Sensorimotor transformation is one of the most fundamental and ubiquitous functions of the central nervous system (CNS). Although the general organization of the locomotor neural circuitry is relatively well understood, less is known about its activation by sensory inputs and its modulation. Utilizing the lamprey model, a detailed understanding of sensorimotor integration in vertebrates is emerging. In this article, we explore how the vertebrate CNS integrates sensory signals to generate motor behavior by examining the pathways and neural mechanisms involved in the transformation of cutaneous and olfactory inputs into motor output in the lamprey. We then review how 5-hydroxytryptamine (5-HT) acts on these systems by modulating both sensory inputs and motor output. A comprehensive review of this fundamental topic should provide a useful framework in the fields of motor control, sensorimotor integration and neuromodulation.
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Affiliation(s)
- Gheylen Daghfous
- Groupe de Recherche en Activité Physique Adaptée, Département des Sciences de l'Activité Physique, Université du Québec à MontréalMontréal, QC, Canada; Groupe de Recherche sur le Système Nerveux Central, Département de Neurosciences, Université de MontréalMontréal, QC, Canada
| | - Warren W Green
- Department of Biological Sciences and Great Lakes Institute for Environmental Research, University of Windsor Windsor, ON, Canada
| | - Simon T Alford
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago Chicago, IL, USA
| | - Barbara S Zielinski
- Department of Biological Sciences and Great Lakes Institute for Environmental Research, University of Windsor Windsor, ON, Canada
| | - Réjean Dubuc
- Groupe de Recherche en Activité Physique Adaptée, Département des Sciences de l'Activité Physique, Université du Québec à MontréalMontréal, QC, Canada; Groupe de Recherche sur le Système Nerveux Central, Département de Neurosciences, Université de MontréalMontréal, QC, Canada
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10
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Cherniak M, Etlin A, Strauss I, Anglister L, Lev-Tov A. The sacral networks and neural pathways used to elicit lumbar motor rhythm in the rodent spinal cord. Front Neural Circuits 2014; 8:143. [PMID: 25520624 PMCID: PMC4253665 DOI: 10.3389/fncir.2014.00143] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 11/11/2014] [Indexed: 01/17/2023] Open
Abstract
Identification of neural networks and pathways involved in activation and modulation of spinal central pattern generators (CPGs) in the absence of the descending control from the brain is important for further understanding of neural control of movement and for developing innovative therapeutic approaches to improve the mobility of spinal cord injury patients. Activation of the hindlimb innervating segments by sacrocaudal (SC) afferent input and by specific application of neurochemicals to the sacral networks is feasible in the isolated spinal cord preparation of the newborn rat. Here we review our recent studies of sacral relay neurons with lumbar projections and evaluate their role in linking the sacral and thoracolumbar (TL) networks during different motor behaviors. Our major findings show that: (1) heterogeneous groups of dorsal, intermediate and ventral sacral-neurons with ventral and lateral ascending funicular projections mediate the activation of the locomotor CPGs through sacral sensory input; and (2) rhythmic excitation of lumbar flexor motoneurons, produced by bath application of alpha-1 adrenoceptor agonists to the sacral segments is mediated exclusively by ventral clusters of sacral-neurons with lumbar projections through the ventral funiculus.
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Affiliation(s)
- Meir Cherniak
- Department of Medical Neurobiology, Institute for Medical Research-Israel-Canada, IMRIC, The Hebrew University Medical School Jerusalem, Israel
| | - Alex Etlin
- Department of Medical Neurobiology, Institute for Medical Research-Israel-Canada, IMRIC, The Hebrew University Medical School Jerusalem, Israel
| | - Ido Strauss
- Department of Medical Neurobiology, Institute for Medical Research-Israel-Canada, IMRIC, The Hebrew University Medical School Jerusalem, Israel
| | - Lili Anglister
- Department of Medical Neurobiology, Institute for Medical Research-Israel-Canada, IMRIC, The Hebrew University Medical School Jerusalem, Israel
| | - Aharon Lev-Tov
- Department of Medical Neurobiology, Institute for Medical Research-Israel-Canada, IMRIC, The Hebrew University Medical School Jerusalem, Israel
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11
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Alford ST, Alpert MH. A synaptic mechanism for network synchrony. Front Cell Neurosci 2014; 8:290. [PMID: 25278839 PMCID: PMC4166887 DOI: 10.3389/fncel.2014.00290] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 08/31/2014] [Indexed: 01/06/2023] Open
Abstract
Within neural networks, synchronization of activity is dependent upon the synaptic connectivity of embedded microcircuits and the intrinsic membrane properties of their constituent neurons. Synaptic integration, dendritic Ca2+ signaling, and non-linear interactions are crucial cellular attributes that dictate single neuron computation, but their roles promoting synchrony and the generation of network oscillations are not well understood, especially within the context of a defined behavior. In this regard, the lamprey spinal central pattern generator (CPG) stands out as a well-characterized, conserved vertebrate model of a neural network (Smith et al., 2013a), which produces synchronized oscillations in which neural elements from the systems to cellular level that control rhythmic locomotion have been determined. We review the current evidence for the synaptic basis of oscillation generation with a particular emphasis on the linkage between synaptic communication and its cellular coupling to membrane processes that control oscillatory behavior of neurons within the locomotor network. We seek to relate dendritic function found in many vertebrate systems to the accessible lamprey central nervous system in which the relationship between neural network activity and behavior is well understood. This enables us to address how Ca2+ signaling in spinal neuron dendrites orchestrate oscillations that drive network behavior.
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Affiliation(s)
- Simon T Alford
- Department of Biological Sciences, University of Illinois at Chicago Chicago, IL, USA
| | - Michael H Alpert
- Department of Biological Sciences, University of Illinois at Chicago Chicago, IL, USA
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12
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Synaptic NMDA receptor-dependent Ca²⁺ entry drives membrane potential and Ca²⁺ oscillations in spinal ventral horn neurons. PLoS One 2013; 8:e63154. [PMID: 23646190 PMCID: PMC3640011 DOI: 10.1371/journal.pone.0063154] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 03/28/2013] [Indexed: 11/28/2022] Open
Abstract
During vertebrate locomotion, spinal neurons act as oscillators when initiated by glutamate release from descending systems. Activation of NMDA receptors initiates Ca2+-mediated intrinsic membrane potential oscillations in central pattern generator (CPG) neurons. NMDA receptor-dependent intrinsic oscillations require Ca2+-dependent K+ (KCa2) channels for burst termination. However, the location of Ca2+ entry mediating KCa2 channel activation, and type of Ca2+ channel – which includes NMDA receptors and voltage-gated Ca2+ channels (VGCCs) – remains elusive. NMDA receptor-dependent Ca2+ entry necessitates presynaptic release of glutamate, implying a location at active synapses within dendrites, whereas VGCC-dependent Ca2+ entry is not similarly constrained. Where Ca2+ enters relative to KCa2 channels is crucial to information processing of synaptic inputs necessary to coordinate locomotion. We demonstrate that Ca2+ permeating NMDA receptors is the dominant source of Ca2+ during NMDA-dependent oscillations in lamprey spinal neurons. This Ca2+ entry is synaptically located, NMDA receptor-dependent, and sufficient to activate KCa2 channels at excitatory interneuron synapses onto other CPG neurons. Selective blockade of VGCCs reduces whole-cell Ca2+ entry but leaves membrane potential and Ca2+ oscillations unaffected. Furthermore, repetitive oscillations are prevented by fast, but not slow, Ca2+ chelation. Taken together, these results demonstrate that KCa2 channels are closely located to NMDA receptor-dependent Ca2+ entry. The close spatial relationship between NMDA receptors and KCa2 channels provides an intrinsic mechanism whereby synaptic excitation both excites and subsequently inhibits ventral horn neurons of the spinal motor system. This places the components necessary for oscillation generation, and hence locomotion, at glutamatergic synapses.
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13
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Telles SCL, Alves RSC, Chadi G. Spinal cord injury as a trigger to develop periodic leg movements during sleep: an evolutionary perspective. ARQUIVOS DE NEURO-PSIQUIATRIA 2013; 70:880-4. [PMID: 23175202 DOI: 10.1590/s0004-282x2012001100011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 04/13/2012] [Indexed: 12/17/2022]
Abstract
The primary trigger to periodic limb movement (PLM) during sleep is still unknown. Its association with the restless legs syndrome (RLS) is established in humans and was reported in spinal cord injury (SCI) patients classified by the American Spinal Injury Association (ASIA) as A. Its pathogenesis has not been completely unraveled, though recent advances might enhance our knowledge about those malfunctions. PLM association with central pattern generator (CPG) is one of the possible pathologic mechanisms involved. This article reviewed the advances in PLM and RLS genetics, the evolution of CPG functioning, and the neurotransmitters involved in CPG, PLM and RLS. We have proposed that SCI might be a trigger to develop PLM.
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Affiliation(s)
- Susana Cristina Lerosa Telles
- Neuroregeneration Center, Experimental Neurology, Department of Neurology, School of Medicine, Universidade de São Paulo, São Paulo SP, Brazil.
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14
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Wu G, Perlmutter SI. Sensitivity of spinal neurons to GABA and glycine during voluntary movement in behaving monkeys. J Neurophysiol 2012; 109:193-201. [PMID: 23076104 DOI: 10.1152/jn.01081.2011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
GABAergic and glycinergic inhibition play key roles in the function of spinal motor pathways. However, there is little direct information on the extent to which inhibition controls the activity of spinal neurons during behavior or the relative effectiveness of GABA and glycine on cell activity under normal conditions. These issues were investigated in three macaque monkeys trained to perform voluntary ramp-and-hold wrist movements and grip. Pipettes with an extracellular recording electrode and iontophoresis barrels were used to eject GABA, glycine, and/or their respective antagonists, bicuculline and strychnine, as the activity of single neurons was recorded in the C6-T1 spinal segments during hand movements. The firing rate of the vast majority of neurons decreased when an inhibitory neurotransmitter was ejected from the electrode, suggesting that most movement-related spinal neurons are sensitive to both GABA and glycine. Most movement-related neurons exhibited increased activity during iontophoresis of an antagonist, suggesting that both GABAergic and glycinergic inhibition actively regulate the majority of spinal neurons during movement. These conclusions were supported by the responses of neurons tested with both agonists or both antagonists. Bicuculline and strychnine produced the largest increases in firing rate during dynamic movements (ramp phase), smaller increases during maintained torque/force (hold phase), and the smallest increase during the rest period. Since excitatory inputs also tend to increase progressively from rest to static to dynamic muscle contractions, this result is consistent with coupled excitatory and inhibitory inputs to spinal neurons during movement.
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Affiliation(s)
- Guoji Wu
- Department of Physiology & Biophysics, Washington National Primate Research Center, University of Washington, Seattle, Washington 98195, USA
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Ireland MF, Funk GD, Bellingham MC. Muscarinic acetylcholine receptors enhance neonatal mouse hypoglossal motoneuron excitability in vitro. J Appl Physiol (1985) 2012; 113:1024-39. [DOI: 10.1152/japplphysiol.00699.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
In brain stem slices from neonatal ( postnatal days 0–4) CD-1 mice, muscarinic ACh receptors (MAChRs) increased rhythmic inspiratory-related and tonic hypoglossal nerve discharge and depolarized single hypoglossal motoneurons (HMs) via an inward current without changing input resistance. These responses were blocked by the MAChR antagonist 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide (4-DAMP; 100 nM). MAChRs shifted voltage-dependent activation of the hyperpolarization-activated cation current to more positive levels. MAChRs increased the HM repetitive firing rate and decreased rheobase, with both effects being blocked by 4-DAMP. Muscarinic agonists reduced the afterhyperpolarization of single action potentials (APs), suggesting that small-conductance Ca2+-dependent K+ current inhibition increased the HM firing rate. Muscarinic agonists also reduced the AP amplitude and slowed its time course, suggesting that MAChRs inhibited voltage-gated Na+ channels. To compare muscarinic excitation of single HMs to muscarinic excitatory effects on motor output in thicker brain stem slices requiring higher extracellular K+ for rhythmic activity, we tested the effects of muscarinic agonists on single HM excitability in high-K+ artificial cerebrospinal fluid (aCSF). In high-K+ aCSF, muscarinic agonists still depolarized HMs and altered AP size and shape, as in standard aCSF, but did not increase the steady-state firing rate, decrease afterhyperpolarization, or alter threshold potential. These results indicate that the basic cellular response of HMs to muscarinic receptors is excitatory, via a number of distinct mechanisms, and that this excitatory response will be largely preserved in rhythmically active brain stem slices.
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Affiliation(s)
- Matthew F. Ireland
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia; and
| | - Gregory D. Funk
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Mark C. Bellingham
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia; and
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Jinks SL, Andrada J. Validation and Insights of Anesthetic Action in an Early Vertebrate Network. Anesth Analg 2011; 113:1033-42. [DOI: 10.1213/ane.0b013e3182273c34] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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β-pompilidotoxin modulates spontaneous activity and persistent sodium currents in spinal networks. Neuroscience 2010; 172:129-38. [PMID: 20955768 DOI: 10.1016/j.neuroscience.2010.10.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 10/07/2010] [Accepted: 10/08/2010] [Indexed: 02/07/2023]
Abstract
The origin of rhythm generation in mammalian spinal cord networks is still poorly understood. In a previous study, we showed that spontaneous activity in spinal networks takes its origin in the properties of certain intrinsically spiking interneurons based on the persistent sodium current (INaP). We also showed that depolarization block caused by a fast inactivation of the transient sodium current (INaT) contributes to the generation of oscillatory activity in spinal cord cultures. Recently, a toxin called beta-pompilidotoxin (β-PMTX) that slows the inactivation process of tetrodotoxin (TTX)-sensitive sodium channels has been extracted from the solitary wasp venom. In the present study, we therefore investigated the effect of β-PMTX on rhythm generation and on sodium currents in spinal networks. Using intracellular recordings and multielectrode array (MEA) recordings in dissociated spinal cord cultures from embryonic (E14) rats, we found that β-PMTX reduces the number of population bursts and increases the background asynchronous activity. We then uncoupled the network by blocking all synaptic transmission (APV, CNQX, bicuculline and strychnine) and observed that β-PMTX increases both the intrinsic activity at individual channels and the number of intrinsically activated channels. At the cellular level, we found that β-PMTX has two effects: it switches 58% of the silent interneurons into spontaneously active interneurons and increases the firing rate of intrinsically spiking cells. Finally, we investigated the effect of β-PMTX on sodium currents. We found that this toxin not only affects the inactivation of INaT but also increases the peak amplitude of the persistent sodium current (INaP). Altogether, theses findings suggest that β-PMTX acting on INaP and INaT enhances intrinsic activity leading to a profound modulation of spontaneous rhythmic activity in spinal networks.
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Horie T, Nakagawa M, Sasakura Y, Kusakabe TG, Tsuda M. Simple motor system of the ascidian larva: neuronal complex comprising putative cholinergic and GABAergic/glycinergic neurons. Zoolog Sci 2010; 27:181-90. [PMID: 20141423 DOI: 10.2108/zsj.27.181] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The ascidian larva is an excellent model for studies of the functional organization and neuronal circuits of chordates due to its remarkably simple central nervous system (CNS), comprised of about 100 neurons. To date, however, the identities of the various neurons in the ascidian larva, particularly their neurotransmitter phenotypes, are not well established. Acetylcholine, GABA, and glycine are critical neurotransmitters for locomotion in many animals. We visualized putative cholinergic neurons and GABAergic/glycinergic neurons in the ascidian larva by immunofluorescent staining using antibodies against vesicular acetylcholine transporter (VACHT) and vesicular GABA/glycine transporter (VGAT), respectively. Neurons expressing a cholinergic phenotype were found in the brain vesicle and the visceral ganglion. Five pairs of VACHT-positive neurons were located in the visceral ganglion. These putative cholinergic neurons extended their axons posteriorly and formed nerve terminals proximal to the most anterior muscle cells in the tail. VGAT-positive neurons were located in the brain vesicle, the visceral ganglion, and the anterior nerve cord. Two distinct pairs of VGAT-positive neurons, bilaterally aligned along the anterior nerve cord, extended axons anteriorly, near to the axons of the contralateral VACHT-positive neurons. Cell bodies of the VGAT-positive neurons lay on these nerve tracts. The neuronal complex, comprising motor neurons with a cholinergic phenotype and some of the GABA/glycinergic interneurons, has structural features that are compatible with a central pattern generator (CPG) producing a rhythmic movement of the tail. The simple CPG of the ascidian larva may represent the ancestral state of the vertebrate motor system.
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Affiliation(s)
- Takeo Horie
- Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako-gun, Hyogo 678-1297, Japan.
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19
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Guertin PA. The mammalian central pattern generator for locomotion. ACTA ACUST UNITED AC 2009; 62:45-56. [DOI: 10.1016/j.brainresrev.2009.08.002] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Revised: 08/21/2009] [Accepted: 08/24/2009] [Indexed: 02/09/2023]
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21
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Yew JY, Wang Y, Barteneva N, Dikler S, Kutz-Naber KK, Li L, Kravitz EA. Analysis of neuropeptide expression and localization in adult drosophila melanogaster central nervous system by affinity cell-capture mass spectrometry. J Proteome Res 2009; 8:1271-84. [PMID: 19199706 DOI: 10.1021/pr800601x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A combined approach using mass spectrometry, a novel neuron affinity capture technique, and Drosophila melanogaster genetic manipulation has been developed to characterize the expression and localization of neuropeptides in the adult D. melanogaster brain. In extract from the whole adult brain, 42 neuropeptides from 18 peptide families were sequenced. Neuropeptide profiling also was performed on targeted populations of cells which were enriched with immunoaffinity purification using a genetically expressed marker.
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Affiliation(s)
- Joanne Y Yew
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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22
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Horie T, Nakagawa M, Sasakura Y, Kusakabe TG. Cell type and function of neurons in the ascidian nervous system. Dev Growth Differ 2009; 51:207-20. [PMID: 19379276 DOI: 10.1111/j.1440-169x.2009.01105.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Ascidians, or sea squirts, are primitive chordates, and their tadpole larvae share a basic body plan with vertebrates, including a notochord and a dorsal tubular central nervous system (CNS). The CNS of the ascidian larva is formed through a process similar to vertebrate neurulation, while the ascidian CNS is remarkably simple, consisting of about 100 neurons. Recent identification of genes that are specifically expressed in a particular subtype of neurons has enabled us to reveal neuronal networks at single-cell resolution. Based on the information on neuron subtype-specific genes, different populations of neurons have been visualized by whole-mount in situ hybridization, immunohistochemical staining using specific antibodies, and fluorescence labeling of cell bodies and neurites by a fluorescence protein reporter driven by neuron-specific promoters. Neuronal populations that have been successfully visualized include glutamatergic, cholinergic, gamma-aminobutyric acid/glycinergic, and dopaminergic neurons, which have allowed us to propose functional regionalization of the CNS and a neural circuit for locomotion. Thus, the simple nervous system of the ascidian larva can serve as an attractive model system for studying the development, function, and evolution of the chordate nervous system.
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Affiliation(s)
- Takeo Horie
- Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda, Shizuoka, 415-0025, Japan.
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Sibilla S, Ballerini L. GABAergic and glycinergic interneuron expression during spinal cord development: dynamic interplay between inhibition and excitation in the control of ventral network outputs. Prog Neurobiol 2009; 89:46-60. [PMID: 19539686 DOI: 10.1016/j.pneurobio.2009.06.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Revised: 04/10/2009] [Accepted: 06/09/2009] [Indexed: 11/28/2022]
Abstract
A key objective of neuroscience research is to understand the processes leading to mature neural circuitries in the central nervous system (CNS) that enable the control of different behaviours. During development, network-constitutive neurons undergo dramatic rearrangements, involving their intrinsic properties, such as the blend of ion channels governing their firing activity, and their synaptic interactions. The spinal cord is no exception to this rule; in fact, in the ventral horn the maturation of motor networks into functional circuits is a complex process where several mechanisms cooperate to achieve the development of motor control. Elucidating such a process is crucial in identifying neurons more vulnerable to degenerative or traumatic diseases or in developing new strategies aimed at rebuilding damaged tissue. The focus of this review is on recent advances in understanding the spatio-temporal expression of the glycinergic/GABAergic system and on the contribution of this system to early network function and to motor pattern transformation along with spinal maturation. During antenatal development, the operation of mammalian spinal networks strongly depends on the activity of glycinergic/GABAergic neurons, whose action is often excitatory until shortly before birth when locomotor networks acquire the ability to generate alternating motor commands between flexor and extensor motor neurons. At this late stage of prenatal development, GABA-mediated excitation is replaced by synaptic inhibition mediated by glycine and/or GABA. At this stage of spinal maturation, the large majority of GABAergic neurons are located in the dorsal horn. We propose that elucidating the role of inhibitory systems in development will improve our knowledge on the processes regulating spinal cord maturation.
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Affiliation(s)
- Sara Sibilla
- Life Science Department, Center for Neuroscience B.R.A.I.N., University of Trieste, via Fleming 22, 34127 Trieste, Italy
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Volatile anesthetic effects on midbrain-elicited locomotion suggest that the locomotor network in the ventral spinal cord is the primary site for immobility. Anesthesiology 2008; 108:1016-24. [PMID: 18497602 DOI: 10.1097/aln.0b013e3181730297] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Volatile anesthetics produce immobility primarily by action in the spinal cord; however, anesthetic effects among different neuronal classes located in different spinal regions, and how they relate to immobility, are not understood. METHODS In decerebrated rats, effects of isoflurane and halothane on movement elicited by electrical microstimulation of the mesencephalic locomotor region (MLR) were assessed in relation to minimum alveolar concentration (MAC). Anesthetic effects on step frequency and isometric limb force were measured. The authors also examined effects of MLR stimulation on responses of nociceptive dorsal horn neurons and limb force responses to tail clamp. RESULTS Mean isoflurane requirements to block MLR-elicited stepping were slightly but significantly greater than MAC by 10%. Mean halothane requirements to block MLR-elicited stepping were greater than those for isoflurane and exceeded MAC by 20%. From 0.4 to 1.3 MAC (but not 0.0 to 0.4 MAC), there was a dose-dependent reduction in the frequency and force of hind limb movements elicited by MLR stimulation during both anesthetics. MLR stimulation inhibited noxious stimulus evoked responses of dorsal horn neurons by approximately 80%. Aptly, MLR stimulation produced analgesia that outlasted the midbrain stimulus by at least 15 s, as indicated by an 81% reduction in hind limb force elicited noxious tail clamp. CONCLUSIONS Because electrical stimulation of the MLR elicits movement independent of dorsal horn activation, the immobilizing properties of isoflurane and halothane are largely independent of action in the dorsal horn. The results suggest that volatile anesthetics produce immobility mainly by action on ventral spinal locomotor networks.
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25
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Descending command systems for the initiation of locomotion in mammals. ACTA ACUST UNITED AC 2008; 57:183-91. [DOI: 10.1016/j.brainresrev.2007.07.019] [Citation(s) in RCA: 292] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Accepted: 07/11/2007] [Indexed: 01/09/2023]
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Kirby MS, Nusbaum MP. Peptide hormone modulation of a neuronally modulated motor circuit. J Neurophysiol 2007; 98:3206-20. [PMID: 17913987 DOI: 10.1152/jn.00795.2006] [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] [Indexed: 11/22/2022] Open
Abstract
Rhythmically active motor circuits are influenced by neuronally released and circulating hormone modulators, but there are few systems in which the influence of a peptide hormone modulator on a neuronally modulated motor circuit has been determined. We performed such an analysis in the isolated crab stomatogastric nervous system by assessing the influence of the hormone crustacean cardioactive peptide (CCAP) on the gastric mill (chewing) rhythm elicited by identified modulatory projection neurons. The gastric mill circuit is located in the stomatogastric ganglion. In situ, this ganglion is located within the ophthalmic artery and thus is in the path of circulating hormones such as CCAP. Focally-applied CCAP directly excited some gastric mill neurons, including the gastric mill central pattern generator neurons LG and Int1, but it did not elicit a sustained gastric mill rhythm. At concentrations as low as 10(-10) M, however, CCAP did influence gastric mill rhythms elicited by coactivating the projection neurons MCN1 and CPN2 and by selectively stimulating MCN1. In both cases, CCAP slowed this rhythm by selectively prolonging the protraction phase, although its influence on the MCN1-elicited rhythm was limited to those with relatively brief cycle periods. Interestingly, CCAP also reduced the threshold MCN1 firing frequency for activating the gastric mill rhythm. Last, the gastric mill neurons that exhibited altered activity during these CCAP-influenced rhythms did not correspond completely to the set of CCAP-responsive neurons. These results highlight the ability of hormonal modulation to enhance the flexibility provided by the neuronal modulation of rhythmically active motor circuits.
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Affiliation(s)
- Matthew S Kirby
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6074, USA
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Ibáñez-Sandoval O, Carrillo-Reid L, Galarraga E, Tapia D, Mendoza E, Gomora JC, Aceves J, Bargas J. Bursting in substantia nigra pars reticulata neurons in vitro: possible relevance for Parkinson disease. J Neurophysiol 2007; 98:2311-23. [PMID: 17715194 DOI: 10.1152/jn.00620.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Projection neurons of the substantia nigra reticulata (SNr) convey basal ganglia (BG) processing to thalamocortical and brain stem circuits responsible for movement. Two models try to explain pathological BG performance during Parkinson disease (PD): the rate model, which posits an overexcitation of SNr neurons due to hyperactivity in the indirect pathway and hypoactivity of the direct pathway, and the oscillatory model, which explains PD as the product of pathological pattern generators disclosed by dopamine reduction. These models are, apparently, incompatible. We tested the predictions of the rate model by increasing the excitatory drive and reducing the inhibition on SNr neurons in vitro. This was done pharmacologically with bath application of glutamate agonist N-methyl-d-aspartate and GABA(A) receptor blockers, respectively. Both maneuvers induced bursting behavior in SNr neurons. Therefore synaptic changes forecasted by the rate model induce the electrical behavior predicted by the oscillatory model. In addition, we found evidence that Ca(V)3.2 Ca(2+) channels are a critical step in generating the bursting firing pattern in SNr neurons. Other ion channels involved are: hyperpolarization-activated cation channels, high-voltage-activated Ca(2+) channels, and Ca(2+)-activated K(+) channels. However, although these channels shape the temporal structure of bursting, only Ca(V)3.2 Ca(2+) channels are indispensable for the initiation of the bursting pattern.
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Affiliation(s)
- Osvaldo Ibáñez-Sandoval
- Departamento de Biofísica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City, México
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El Manira A, Kyriakatos A, Nanou E, Mahmood R. Endocannabinoid signaling in the spinal locomotor circuitry. ACTA ACUST UNITED AC 2007; 57:29-36. [PMID: 17719648 DOI: 10.1016/j.brainresrev.2007.06.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Accepted: 06/26/2007] [Indexed: 11/25/2022]
Abstract
To understand how the spinal central pattern generators produce locomotor movements, it is necessary to characterize the network's connectivity, the intrinsic properties of the constituent neurons and the modulatory mechanisms. Modulation operating within spinal locomotor networks is required for the generation of the final motor output. In this review, we have summarized how endocannabinoids released by locomotor network neurons contribute to setting the baseline locomotor frequency. They are synthesized on demand as a result of activation of mGluR1 and act as retrograde messengers to depress inhibitory synaptic transmission. We also discuss how endogenous activation of mGluR1 contributes to the normal operation of the spinal locomotor network and the underlying cellular and synaptic mechanisms.
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Affiliation(s)
- Abdeljabbar El Manira
- Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
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29
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Huynh P, Boyd SK. Nitric Oxide Synthase and NADPH Diaphorase Distribution in the Bullfrog (Rana catesbeiana) CNS: Pathways and Functional Implications. BRAIN, BEHAVIOR AND EVOLUTION 2007; 70:145-63. [PMID: 17595535 DOI: 10.1159/000104306] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Accepted: 11/07/2006] [Indexed: 11/19/2022]
Abstract
The gas nitric oxide (NO) is emerging as an important regulator of normal physiology and pathophysiology in the central nervous system (CNS). The distribution of cells releasing NO is poorly understood in non-mammalian vertebrates. Nitric oxide synthase immunocytochemistry (NOS ICC) was thus used to identify neuronal cells that contain the enzyme required for NO production in the amphibian brain and spinal cord. NADPH-diaphorase (NADPHd) histochemistry was also used because the presence of NADPHd serves as a reliable indicator of nitrergic cells. Both techniques revealed stained cells in all major structures and pathways in the bullfrog brain. Staining was identified in the olfactory glomeruli, pallium and subpallium of the telencephalon; epithalamus, thalamus, preoptic area, and hypothalamus of the diencephalon; pretectal area, optic tectum, torus semicircularis, and tegmentum of the mesencephalon; all layers of the cerebellum; reticular formation; nucleus of the solitary tract, octaval nuclei, and dorsal column nuclei of the medulla; and dorsal and motor fields of the spinal cord. In general, NADPHd histochemistry provided better staining quality, especially in subpallial regions, although NOS ICC tended to detect more cells in the olfactory bulb, pallium, ventromedial thalamus, and cerebellar Purkinje cell layer. NOS ICC was also more sensitive for motor neurons and consistently labeled them in the vagus nucleus and along the length of the rostral spinal cord. Thus, nitrergic cells were ubiquitously distributed throughout the bullfrog brain and likely serve an essential regulatory function.
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Affiliation(s)
- Phuong Huynh
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
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Deumens R, Jaken RJP, Marcus MAE, Joosten EAJ. The CatWalk gait analysis in assessment of both dynamic and static gait changes after adult rat sciatic nerve resection. J Neurosci Methods 2007; 164:120-30. [PMID: 17532474 DOI: 10.1016/j.jneumeth.2007.04.009] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Revised: 03/19/2007] [Accepted: 04/13/2007] [Indexed: 10/23/2022]
Abstract
Functional repair of neurotmesis has been proven most challenging in regenerative medicine. Progress in this field has shown that functional repair not only requires axon regeneration, but also selectivity in target reinnervation. Although selectivity in target reinnervation still involves relatively unexplored avenues, evidence-based medicine, in the end, requires behavioral proof of repair. Therefore, there is a need for tests assessing behavioral deficits after neurotmesis. To date, behavioral tests for detecting both dynamic and static parameters are limited. The CatWalk gait analysis has been shown to detect a multitude of speed-controlled dynamic and static gait deficits after experimental spinal cord injury. Therefore, we here evaluated its use in detecting both dynamic and static gait deficits after neurotmesis. After rat sciatic nerve resection CatWalk testing was performed for 8 weeks. A large amount of dynamic and static gait parameters were detected to be immediately and severely affected in the ipsilateral paw, sometimes reaching levels of only 15% of those of the unaffected paw. We conclude that the CatWalk objectively detects dynamic and static gait impairments after sciatic nerve resection and future experiments are now required to prove which of these parameters are of particular interest to detect functional repair.
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Affiliation(s)
- Ronald Deumens
- Department of Anesthesiology, Maastricht University, Maastricht, The Netherlands.
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31
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Maze IS, Wright GA, Mustard JA. Acute ethanol ingestion produces dose-dependent effects on motor behavior in the honey bee (Apis mellifera). JOURNAL OF INSECT PHYSIOLOGY 2006; 52:1243-53. [PMID: 17070538 PMCID: PMC1712673 DOI: 10.1016/j.jinsphys.2006.09.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Revised: 09/05/2006] [Accepted: 09/11/2006] [Indexed: 05/12/2023]
Abstract
Ethanol consumption produces characteristic behavioral states in animals that include sedation, disorientation, and disruption of motor function. Using individual honey bees, we assessed the effects of ethanol ingestion on motor function via continuous observations of their behavior. Consumption of 1 M sucrose solutions containing a range of ethanol doses led to hemolymph ethanol levels of approximately 40-100 mM. Using ethanol doses in this range, we observed time and dose-dependent effects of ethanol on the percent of time our subjects spent walking, stopped, or upside down, and on the duration and frequency of bouts of behavior. The effects on grooming and flying behavior were more complex. Behavioral recovery from ethanol treatment was both time and ethanol dose dependent, occurring between 12 and 24 h post-ingestion for low doses and at 24-48 h for higher doses. Furthermore, the amount of ethanol measured in honey bee hemolymph appeared to correlate with recovery. We predict that the honey bee will prove to be an excellent model system for studying the influence of ethanol on the neural mechanisms underlying behavior.
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Affiliation(s)
- Ian S. Maze
- Department of Entomology, Ohio State University, Columbus, OH 43210
| | - Geraldine A. Wright
- Department of Entomology, Ohio State University, Columbus, OH 43210
- Mathematical Biosciences Institute, Ohio State University, Columbus, OH 43210
| | - Julie A. Mustard
- Department of Entomology, Ohio State University, Columbus, OH 43210
- *To whom correspondence should be addressed:
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32
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Lund JP, Kolta A. Brainstem circuits that control mastication: do they have anything to say during speech? JOURNAL OF COMMUNICATION DISORDERS 2006; 39:381-90. [PMID: 16884732 DOI: 10.1016/j.jcomdis.2006.06.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Accepted: 06/12/2006] [Indexed: 05/11/2023]
Abstract
UNLABELLED Mastication results from the interaction of an intrinsic rhythmical neural pattern and sensory feedback from the mouth, muscles and joints. The pattern is matched to the physical characteristics of food, but also varies with age. There are large differences in masticatory movements among subjects. The intrinsic rhythmical pattern is generated by an assembly of neurons called a central pattern generator (CPG) located in the pons and medulla. The CPG receives inputs from higher centers of the brain, especially from the inferio-lateral region of the sensorimotor cortex and from sensory receptors. Mechanoreceptors in the lips and oral mucosa, in muscles, and in the periodontal ligaments around the roots of the teeth have particularly powerful effects on movement parameters. The central pattern generator includes a core group of neurons with intrinsic bursting properties, as well as a variety of other neurons that receive inputs from oral and muscle spindle afferents. Reorganization of subpopulations of neurons within the CPG underlies changes in movement pattern. In addition to controlling motoneurons supplying the jaw, tongue, and facial muscles, the CPG also modulates reflex circuits. It is proposed that these brainstem circuits also participate in the control of human speech. LEARNING OUTCOMES Readers will be able to: (1) describe the general location and function of the central pattern generator for mastication, (2) identify the primary nuclei involved in the central pattern generator for mastication, (3) describe the general interactions among the central pattern generators of speech, mastication, respiration, and locomotion, and (4) compare/relate the brainstem systems controlling mastication and speech.
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Affiliation(s)
- James P Lund
- Faculty of Dentistry, McGill University, 3640 University Street, Montreal, Que. H3A 2B2, Canada.
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Lund JP, Kolta A. Generation of the Central Masticatory Pattern and Its Modification by Sensory Feedback. Dysphagia 2006; 21:167-74. [PMID: 16897322 DOI: 10.1007/s00455-006-9027-6] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mammalian mastication results from the interaction of an intrinsic rhythmical neural pattern and sensory feedback generated by the interaction of the effecter system (muscles, bones, joints, teeth, soft tissues) with food. The main variables that explain variation in the pattern of human mastication are the subjects themselves, their age, the type of food being eaten, and time during a sequence of movements. The intrinsic pattern of mastication is generated by a central pattern generator (CPG) located in the pons and medulla. The output of the CPG is modified by inputs that descend from higher centers of the brain and by feedback from sensory receptors. Intraoral touch receptors, muscle spindles in the jaw-closing muscles, and specialized mechanoreceptors in the periodontal ligament have especially powerful effects on movement parameters.
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Affiliation(s)
- James P Lund
- Faculty of Dentistry, McGill University, Montreal, Quebec, H3A 2B2, Canada.
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Sieber-Blum M, Schnell L, Grim M, Hu YF, Schneider R, Schwab ME. Characterization of epidermal neural crest stem cell (EPI-NCSC) grafts in the lesioned spinal cord. Mol Cell Neurosci 2006; 32:67-81. [PMID: 16626970 DOI: 10.1016/j.mcn.2006.02.003] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2005] [Revised: 02/14/2006] [Accepted: 02/21/2006] [Indexed: 02/07/2023] Open
Abstract
We have characterized in the contusion-lesioned murine spinal cord the behavior of acutely implanted epidermal neural crest stem cells (EPI-NCSC, formerly eNCSC). EPI-NCSC, a novel type of multipotent adult stem cell, are remnants of the embryonic neural crest. They reside in the bulge of hair follicles and have the ability to differentiate into all major neural crest derivatives (Sieber-Blum, M., Grim, M., Hu, Y.F., Szeder, V., 2004. Pluripotent neural crest stem cells in the adult hair follicle. Dev. Dyn. 231, 258-269). Grafted EPI-NCSC survived, integrated, and intermingled with host neurites in the lesioned spinal cord. EPI-NCSC were non-migratory. They did not proliferate and did not form tumors. Significant subsets expressed neuron-specific beta-III tubulin, the GABAergic marker glutamate decarboxylase 67 (GAD67), the oligodendrocyte marker, RIP, or myelin basic protein (MBP). Close physical association of non-neuronal EPI-NCSC with host neurites was observed. Glial fibrillary acidic protein (GFAP) immunofluorescence was not detected. Collectively, our data indicate that intraspinal EPI-NCSC demonstrate several desirable characteristics that may include local neural replacement and re-myelination.
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Affiliation(s)
- Maya Sieber-Blum
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
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Marina N, Taheri M, Gilbey MP. Generation of a physiological sympathetic motor rhythm in the rat following spinal application of 5-HT. J Physiol 2006; 571:441-50. [PMID: 16396930 PMCID: PMC1796786 DOI: 10.1113/jphysiol.2005.100677] [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: 10/25/2005] [Accepted: 01/04/2006] [Indexed: 11/08/2022] Open
Abstract
When applied in vitro to various CNS structures 5-HT and/or NMDA have been observed to generate rhythmic nervous activity. In contrast, reports of similar in vivo actions are relatively rare. Here we describe a physiological sympathetic motor rhythm regulating the thermoregulatory circulation of the rat tail (T-rhythm; 0.40-1.20 Hz) that can be elicited following intrathecal (i.t.) application of 5-HT to an in situ'isolated' spinal cord preparation (anaesthetized rats spinalized at T10-T11 and cauda equina cut). i.t. injections were delivered to L1 as sympathetic neuronal activity to the tail (SNAT) arises from preganglionic neurones at T11-L2. SNAT was abolished after spinal transection (n = 18) and it did not return spontaneously. The administration of 5-HT (250 nmol) generated rhythmic sympathetic discharges (n = 6). The mean frequency of the T-like rhythm during the highest level of activity was 0.88 +/- 0.04 Hz which was not significantly different from the T-rhythm frequency observed in intact animals (0.77 +/- 0.02 Hz; P > 0.05 n = 16). In contrast, NMDA (1 micromol) generated an irregular tonic activity, but it failed to generate a T-like rhythm (n = 9), even though the mean levels of activity were not significantly different to those produced by 5-HT. However, 5-HT (250 nmol) applied after NMDA generated a T-like rhythm (0.95 +/- 0.11 Hz, n = 6). Our observations support the idea that 5-HT released from rostral ventromedial medullary neurones, known to innervate sympathetic preganglionic neurones, can induce sympathetic rhythmic activity.
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Affiliation(s)
- Nephtali Marina
- Department of Physiology, University College London, Hampstead Campus, London NW3 2PF, UK
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Nistri A, Ostroumov K, Sharifullina E, Taccola G. Tuning and playing a motor rhythm: how metabotropic glutamate receptors orchestrate generation of motor patterns in the mammalian central nervous system. J Physiol 2006; 572:323-34. [PMID: 16469790 PMCID: PMC1779665 DOI: 10.1113/jphysiol.2005.100610] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Repeated motor activities like locomotion, mastication and respiration need rhythmic discharges of functionally connected neurons termed central pattern generators (CPGs) that cyclically activate motoneurons even in the absence of descending commands from higher centres. For motor pattern generation, CPGs require integration of multiple processes including activation of ion channels and transmitter receptors at strategic locations within motor networks. One emerging mechanism is activation of glutamate metabotropic receptors (mGluRs) belonging to group I, while group II and III mGluRs appear to play an inhibitory function on sensory inputs. Group I mGluRs generate neuronal membrane depolarization with input resistance increase and rapid fluctuations in intracellular Ca(2+), leading to enhanced excitability and rhythmicity. While synchronicity is probably due to modulation of inhibitory synaptic transmission, these oscillations occurring in coincidence with strong afferent stimuli or application of excitatory agents can trigger locomotor-like patterns. Hence, mGluR-sensitive spinal oscillators play a role in accessory networks for locomotor CPG activation. In brainstem networks supplying tongue muscle motoneurons, group I receptors facilitate excitatory synaptic inputs and evoke synchronous oscillations which stabilize motoneuron firing at regular, low frequency necessary for rhythmic tongue contractions. In this case, synchronicity depends on the strong electrical coupling amongst motoneurons rather than inhibitory transmission, while cyclic activation of K(ATP) conductances sets its periodicity. Activation of mGluRs is therefore a powerful strategy to trigger and recruit patterned discharges of motoneurons.
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Affiliation(s)
- Andrea Nistri
- Neurobiology Sector, CNR-INFM DEMOCRITOS National Simulation Center, International School for Advanced Studies (SISSA), Trieste, Italy.
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Ramirez JM, Viemari JC. Determinants of inspiratory activity. Respir Physiol Neurobiol 2005; 147:145-57. [PMID: 15964786 DOI: 10.1016/j.resp.2005.05.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 05/06/2005] [Accepted: 05/06/2005] [Indexed: 11/24/2022]
Abstract
In vitro and in vivo studies have identified the pre-Bötzinger complex as an important kernel for the generation of inspiratory activity. The mechanisms underlying inspiratory rhythm generation involve pacemaker as well as synaptic mechanisms. In slice preparations, blockade of pacemaker properties with blockers for the persistent Na+ current, and the Ca2+-activated inward cationic current, abolishes respiratory activity. Here we show that blockade of the persistent Na+ current alone is sufficient to abolish respiratory activity in the in situ preparation. Although pacemaker neurons may be critical for establishing the basic respiratory rhythm, their rhythmic output is modulated by many elements of the respiratory network. For example, levels of synaptic inhibition control whether they burst or not, and endogenously released neuromodulators, such as serotonin and substance P modulate their intrinsic membrane currents. We hypothesize that the balance between synaptic and intrinsic pacemaker properties in the respiratory network is plastic, and that alterations of this balance may lead to dynamic reconfigurations of the respiratory network, which ultimately give rise to different activity patterns.
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Affiliation(s)
- Jan-Marino Ramirez
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, IL 60637, USA.
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Adaption of the central masticatory pattern to the biomechanical properties of food. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.ics.2005.07.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
Recent studies have implicated a number of membrane-associated proteins, including the signaling pair neuroligin and beta-neurexin, in synapse formation, suggesting that they govern the ratio of inhibitory and excitatory synapses on CNS neurons. These findings, together with data indicating that the genes encoding neuroligin and PSD95 are altered in autism patients, suggest that a molecular understanding of complex neurological diseases is within reach.
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Affiliation(s)
- Hollis Cline
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, NY 11724, USA.
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Liu J, Jordan LM. Stimulation of the parapyramidal region of the neonatal rat brain stem produces locomotor-like activity involving spinal 5-HT7 and 5-HT2A receptors. J Neurophysiol 2005; 94:1392-404. [PMID: 15872068 DOI: 10.1152/jn.00136.2005] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Locomotion can be induced in rodents by direct application 5-hydroxytryptamine (5-HT) onto the spinal cord. Previous studies suggest important roles for 5-HT7 and 5-HT2A receptors in the locomotor effects of 5-HT. Here we show for the first time that activation of a discrete population of 5-HT neurons in the rodent brain stem produces locomotion and that the evoked locomotion requires 5-HT7 and 5-HT2A receptors. Cells localized in the parapyramidal region (PPR) of the mid-medulla produced locomotor-like activity as a result of either electrical or chemical stimulation, and PPR-evoked locomotor-like activity was blocked by antagonists to 5-HT2A and 5-HT7 receptors located on separate populations of neurons concentrated in different rostro-caudal regions. 5-HT7 receptor antagonists blocked locomotor-like activity when applied above the L3 segment; 5-HT2A receptor antagonists blocked locomotor-like activity only when applied below the L2 segment. 5-HT7 receptor antagonists decreased step cycle duration, consistent with an action on neurons involved in the rhythm-generating function of the central pattern generator (CPG) for locomotion. 5-HT2A antagonists reduced the amplitude of ventral root activity with only small effects on step cycle duration, suggesting an action directly on cells involved in the output stage of the pattern generator for locomotion, including motoneurons and premotor cells. Experiments with selective antagonists show that dopaminergic (D1, D2) and noradrenergic (alpha1, alpha2) receptors are not critical for PPR-evoked locomotor-like activity.
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Affiliation(s)
- Jun Liu
- Department of Physiology, Spinal Cord Research Centre, University of Manitoba Winnipeg, Winnipeg, Canada
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Kettunen P, Kyriakatos A, Hallén K, El Manira A. Neuromodulation via conditional release of endocannabinoids in the spinal locomotor network. Neuron 2005; 45:95-104. [PMID: 15629705 DOI: 10.1016/j.neuron.2004.12.022] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Revised: 06/24/2004] [Accepted: 11/15/2004] [Indexed: 10/26/2022]
Abstract
Endocannabinoids act as retrograde signals to modulate synaptic transmission. Little is known, however, about their significance in integrated network activity underlying motor behavior. We have examined the physiological effects of endocannabinoids in a neuronal network underlying locomotor behavior using the isolated lamprey spinal cord. Our results show that endocannabinoids are released during locomotor activity and participate in setting the baseline burst rate. They are released in response to mGluR1 activation and act as retrograde messengers. This conditional release of endocannabinoids can transform motoneurons and crossing interneurons into modulatory neurons by enabling them to regulate their inhibitory synaptic inputs and thus contribute to the modulation of the locomotor burst frequency. These results provide evidence that endocannabinoid retrograde signaling occurs within the locomotor network and contributes to motor pattern generation and regulation in the spinal cord.
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Affiliation(s)
- Petronella Kettunen
- Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
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Schwartz EJ, Gerachshenko T, Alford S. 5-HT Prolongs Ventral Root Bursting Via Presynaptic Inhibition of Synaptic Activity During Fictive Locomotion in Lamprey. J Neurophysiol 2005; 93:980-8. [PMID: 15456802 DOI: 10.1152/jn.00669.2004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Locomotor pattern generation is maintained by integration of the intrinsic properties of spinal central pattern generator (CPG) neurons in conjunction with synaptic activity of the neural network. In the lamprey, the spinal locomotor CPG is modulated by 5-HT. On a cellular level, 5-HT presynaptically inhibits synaptic transmission and postsynaptically inhibits a Ca2+-activated K+current responsible for the slow afterhyperpolarization (sAHP) that follows action potentials in ventral horn neurons. To understand the contribution of these cellular mechanisms to the modulation of the spinal CPG, we have tested the effect of selective 5-HT analogues against fictive locomotion initiated by bath application of N-methyl-d-aspartate (NMDA). We found that the 5-HT1Dagonist, L694-247, dramatically prolongs the frequency of ventral root bursting. Furthermore, we show that L694-247 presynaptically inhibits synaptic transmission without altering postsynaptic Ca2+-activated K+currents. We also confirm that 5-HT inhibits synaptic transmission at concentrations that modulate locomotion. To examine the mechanism by which selective presynaptic inhibition modulates the frequency of fictive locomotion, we performed voltage- and current-clamp recordings of CPG neurons during locomotion. Our results show that 5-HT decreases glutamatergic synaptic drive within the locomotor CPG during fictive locomotion. Thus we conclude that presynaptic inhibition of neurotransmitter release contributes to 5-HT–mediated modulation of locomotor activity.
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Affiliation(s)
- Eric J Schwartz
- University of Illinois at Chicago, Department of Biological Sciences, Chicago, IL 60607, USA
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