1
|
Knüsel J, Crespi A, Cabelguen JM, Ijspeert AJ, Ryczko D. Reproducing Five Motor Behaviors in a Salamander Robot With Virtual Muscles and a Distributed CPG Controller Regulated by Drive Signals and Proprioceptive Feedback. Front Neurorobot 2020; 14:604426. [PMID: 33424576 PMCID: PMC7786271 DOI: 10.3389/fnbot.2020.604426] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 11/10/2020] [Indexed: 11/13/2022] Open
Abstract
Diverse locomotor behaviors emerge from the interactions between the spinal central pattern generator (CPG), descending brain signals and sensory feedback. Salamander motor behaviors include swimming, struggling, forward underwater stepping, and forward and backward terrestrial stepping. Electromyographic and kinematic recordings of the trunk show that each of these five behaviors is characterized by specific patterns of muscle activation and body curvature. Electrophysiological recordings in isolated spinal cords show even more diverse patterns of activity. Using numerical modeling and robotics, we explored the mechanisms through which descending brain signals and proprioceptive feedback could take advantage of the flexibility of the spinal CPG to generate different motor patterns. Adapting a previous CPG model based on abstract oscillators, we propose a model that reproduces the features of spinal cord recordings: the diversity of motor patterns, the correlation between phase lags and cycle frequencies, and the spontaneous switches between slow and fast rhythms. The five salamander behaviors were reproduced by connecting the CPG model to a mechanical simulation of the salamander with virtual muscles and local proprioceptive feedback. The main results were validated on a robot. A distributed controller was used to obtain the fast control loops necessary for implementing the virtual muscles. The distributed control is demonstrated in an experiment where the robot splits into multiple functional parts. The five salamander behaviors were emulated by regulating the CPG with two descending drives. Reproducing the kinematics of backward stepping and struggling however required stronger muscle contractions. The passive oscillations observed in the salamander's tail during forward underwater stepping could be reproduced using a third descending drive of zero to the tail oscillators. This reduced the drag on the body in our hydrodynamic simulation. We explored the effect of local proprioceptive feedback during swimming and forward terrestrial stepping. We found that feedback could replace or reduce the need for different drives in both cases. It also reduced the variability of intersegmental phase lags toward values appropriate for locomotion. Our work suggests that different motor behaviors do not require different CPG circuits: a single circuit can produce various behaviors when modulated by descending drive and sensory feedback.
Collapse
Affiliation(s)
- Jérémie Knüsel
- Biorobotics Laboratory (BioRob), Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Institute for Optimisation and Data Analysis (IODA), Bern University of Applied Sciences, Biel, Switzerland
| | - Alessandro Crespi
- Biorobotics Laboratory (BioRob), Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Jean-Marie Cabelguen
- Institut National de la Santé et de la Recherche Médicale (INSERM) U 862 - Neurocentre Magendie, Université de Bordeaux, Bordeaux, France
| | - Auke J Ijspeert
- Biorobotics Laboratory (BioRob), Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Dimitri Ryczko
- Département de Pharmacologie-Physiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada.,Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada.,Institut de Pharmacologie de Sherbrooke, Sherbrooke, QC, Canada.,Centre d'Excellence en Neurosciences de l'Université de Sherbrooke, Sherbrooke, QC, Canada
| |
Collapse
|
2
|
Epidural Stimulation Combined with Triple Gene Therapy for Spinal Cord Injury Treatment. Int J Mol Sci 2020; 21:ijms21238896. [PMID: 33255323 PMCID: PMC7734573 DOI: 10.3390/ijms21238896] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/06/2020] [Accepted: 11/17/2020] [Indexed: 12/18/2022] Open
Abstract
The translation of new therapies for spinal cord injury to clinical trials can be facilitated with large animal models close in morpho-physiological scale to humans. Here, we report functional restoration and morphological reorganization after spinal contusion in pigs, following a combined treatment of locomotor training facilitated with epidural electrical stimulation (EES) and cell-mediated triple gene therapy with umbilical cord blood mononuclear cells overexpressing recombinant vascular endothelial growth factor, glial-derived neurotrophic factor, and neural cell adhesion molecule. Preliminary results obtained on a small sample of pigs 2 months after spinal contusion revealed the difference in post-traumatic spinal cord outcomes in control and treated animals. In treated pigs, motor performance was enabled by EES and the corresponding morpho-functional changes in hind limb skeletal muscles were accompanied by the reorganization of the glial cell, the reaction of stress cell, and synaptic proteins. Our data demonstrate effects of combined EES-facilitated motor training and cell-mediated triple gene therapy after spinal contusion in large animals, informing a background for further animal studies and clinical translation.
Collapse
|
3
|
Fadeev F, Eremeev A, Bashirov F, Shevchenko R, Izmailov A, Markosyan V, Sokolov M, Kalistratova J, Khalitova A, Garifulin R, Islamov R, Lavrov I. Combined Supra- and Sub-Lesional Epidural Electrical Stimulation for Restoration of the Motor Functions after Spinal Cord Injury in Mini Pigs. Brain Sci 2020; 10:brainsci10100744. [PMID: 33081405 PMCID: PMC7650717 DOI: 10.3390/brainsci10100744] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/06/2020] [Accepted: 10/12/2020] [Indexed: 12/20/2022] Open
Abstract
This study evaluates the effect of combined epidural electrical stimulation (EES) applied above (C5) and below (L2) the spinal cord injury (SCI) at T8–9 combined with motor training on the restoration of sensorimotor function in mini pigs. The motor evoked potentials (MEP) induced by EES applied at C5 and L2 levels were recorded in soleus muscles before and two weeks after SCI. EES treatment started two weeks after SCI and continued for 6 weeks led to improvement in multiple metrics, including behavioral, electrophysiological, and joint kinematics outcomes. In control animals after SCI a multiphasic M-response was observed during M/H-response testing, while animals received EES-enable training demonstrated the restoration of the M-response and H-reflex, although at a lower amplitude. The joint kinematic and assessment with Porcine Thoracic Injury Behavior scale (PTIBS) motor recovery scale demonstrated improvement in animals that received EES-enable training compared to animals with no treatment. The positive effect of two-level (cervical and lumbar) epidural electrical stimulation on functional restoration in mini pigs following spinal cord contusion injury in mini pigs could be related with facilitation of spinal circuitry at both levels and activation of multisegmental coordination. This approach can be taken as a basis for the future development of neuromodulation and neurorehabilitation therapy for patients with spinal cord injury.
Collapse
Affiliation(s)
- Filip Fadeev
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Anton Eremeev
- Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia;
| | - Farid Bashirov
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Roman Shevchenko
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Andrei Izmailov
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Vage Markosyan
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Mikhail Sokolov
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Julia Kalistratova
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Anastasiia Khalitova
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Ravil Garifulin
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
| | - Rustem Islamov
- Department of Medical Biology and Genetics, Kazan State Medical University, 420012 Kazan, Russia; (F.F.); (F.B.); (R.S.); (A.I.); (V.M.); (M.S.); (J.K.); (A.K.); (R.G.)
- Correspondence: (R.I.); (I.L.)
| | - Igor Lavrov
- Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia;
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
- Correspondence: (R.I.); (I.L.)
| |
Collapse
|
4
|
Ryczko D, Simon A, Ijspeert AJ. Walking with Salamanders: From Molecules to Biorobotics. Trends Neurosci 2020; 43:916-930. [PMID: 33010947 DOI: 10.1016/j.tins.2020.08.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/12/2020] [Accepted: 08/27/2020] [Indexed: 12/13/2022]
Abstract
How do four-legged animals adapt their locomotion to the environment? How do central and peripheral mechanisms interact within the spinal cord to produce adaptive locomotion and how is locomotion recovered when spinal circuits are perturbed? Salamanders are the only tetrapods that regenerate voluntary locomotion after full spinal transection. Given their evolutionary position, they provide a unique opportunity to bridge discoveries made in fish and mammalian models. Genetic dissection of salamander neural circuits is becoming feasible with new methods for precise manipulation, elimination, and visualisation of cells. These approaches can be combined with classical tools in neuroscience and with modelling and a robotic environment. We propose that salamanders provide a blueprint of the function, evolution, and regeneration of tetrapod locomotor circuits.
Collapse
Affiliation(s)
- Dimitri Ryczko
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada; Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada.
| | - András Simon
- Karolinska Institute, Department of Cell and Molecular Biology, Biomedicum, Solnavägen 9, 17163 Stockholm, Sweden
| | - Auke Jan Ijspeert
- Institute of Bioengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
| |
Collapse
|
5
|
Changes in spinal cord hemodynamics reflect modulation of spinal network with different parameters of epidural stimulation. Neuroimage 2020; 221:117183. [PMID: 32702485 PMCID: PMC7802109 DOI: 10.1016/j.neuroimage.2020.117183] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 06/04/2020] [Accepted: 07/16/2020] [Indexed: 11/29/2022] Open
Abstract
In this study functional ultrasound (fUS) imaging has been implemented to explore the local hemodynamics response induced by electrical epidural stimulation and to study real-time in vivo functional changes of the spinal cord, taking advantage of the superior spatiotemporal resolution provided by fUS. By quantifying the hemodynamics and electromyographic response features, we tested the hypothesis that the temporal hemodynamics response of the spinal cord to electrical epidural stimulation could reflect modulation of the spinal circuitry and accordingly respond to the changes in parameters of electrical stimulation. The results of this study for the first time demonstrate that the hemodynamics response to electrical stimulation could reflect a neural-vascular coupling of the spinal cord. Response in the dorsal areas to epidural stimulation was significantly higher and faster compared to the response in ventral spinal cord. Positive relation between the hemodynamics and the EMG responses was observed at the lower frequencies of epidural stimulation (20 and 40 Hz), which according to our previous findings can facilitate spinal circuitry after spinal cord injury, compared to higher frequencies (200 and 500 Hz). These findings suggest that different mechanisms could be involved in spinal cord hemodynamics changes during different parameters of electrical stimulation and for the first time provide the evidence that neural-vascular coupling of the spinal cord circuitry could be related to specific organization of spinal cord vasculature and hemodynamics.
Collapse
|
6
|
Lavrov I, Fox L, Shen J, Han Y, Cheng J. Gap Junctions Contribute to the Regulation of Walking-Like Activity in the Adult Mudpuppy (Necturus Maculatus). PLoS One 2016; 11:e0152650. [PMID: 27023006 PMCID: PMC4811563 DOI: 10.1371/journal.pone.0152650] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 03/17/2016] [Indexed: 12/03/2022] Open
Abstract
Although gap junctions are widely expressed in the developing central nervous system, the role of electrical coupling of neurons and glial cells via gap junctions in the spinal cord in adults is largely unknown. We investigated whether gap junctions are expressed in the mature spinal cord of the mudpuppy and tested the effects of applying gap junction blocker on the walking-like activity induced by NMDA or glutamate in an in vitro mudpuppy preparation. We found that glial and neural cells in the mudpuppy spinal cord expressed different types of connexins that include connexin 32 (Cx32), connexin 36 (Cx36), connexin 37 (Cx37), and connexin 43 (Cx43). Application of a battery of gap junction blockers from three different structural classes (carbenexolone, flufenamic acid, and long chain alcohols) substantially and consistently altered the locomotor-like activity in a dose-dependent manner. In contrast, these blockers did not significantly change the amplitude of the dorsal root reflex, indicating that gap junction blockers did not inhibit neuronal excitability nonselectively in the spinal cord. Taken together, these results suggest that gap junctions play a significant modulatory role in the spinal neural networks responsible for the generation of walking-like activity in the adult mudpuppy.
Collapse
Affiliation(s)
- Igor Lavrov
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia
| | - Lyle Fox
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Jun Shen
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Yingchun Han
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Jianguo Cheng
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- * E-mail:
| |
Collapse
|
7
|
Lavrov I, Gerasimenko Y, Burdick J, Zhong H, Roy RR, Edgerton VR. Integrating multiple sensory systems to modulate neural networks controlling posture. J Neurophysiol 2015; 114:3306-14. [PMID: 26445868 DOI: 10.1152/jn.00583.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/05/2015] [Indexed: 01/03/2023] Open
Abstract
In this study we investigated the ability of sensory input to produce tonic responses in hindlimb muscles to facilitate standing in adult spinal rats and tested two hypotheses: 1) whether the spinal neural networks below a complete spinal cord transection can produce tonic reactions by activating different sensory inputs and 2) whether facilitation of tonic and rhythmic responses via activation of afferents and with spinal cord stimulation could engage similar neuronal mechanisms. We used a dynamically controlled platform to generate vibration during weight bearing, epidural stimulation (at spinal cord level S1), and/or tail pinching to determine the postural control responses that can be generated by the lumbosacral spinal cord. We observed that a combination of platform displacement, epidural stimulation, and tail pinching produces a cumulative effect that progressively enhances tonic responses in the hindlimbs. Tonic responses produced by epidural stimulation alone during standing were represented mainly by monosynaptic responses, whereas the combination of epidural stimulation and tail pinching during standing or epidural stimulation during stepping on a treadmill facilitated bilaterally both monosynaptic and polysynaptic responses. The results demonstrate that tonic muscle activity after complete spinal cord injury can be facilitated by activation of specific combinations of afferent inputs associated with load-bearing proprioception and cutaneous input in the presence of epidural stimulation and indicate that whether activation of tonic or rhythmic responses is generated depends on the specific combinations of sources and types of afferents activated in the hindlimb muscles.
Collapse
Affiliation(s)
- I Lavrov
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; and
| | - Y Gerasimenko
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Pavlov Institute of Physiology, St. Petersburg, Russia; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; and
| | - J Burdick
- Bioengineering, California Institute of Technology, Pasadena, California
| | - H Zhong
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California
| | - R R Roy
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California
| | - V R Edgerton
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California
| |
Collapse
|
8
|
Bicanski A, Ryczko D, Knuesel J, Harischandra N, Charrier V, Ekeberg Ö, Cabelguen JM, Ijspeert AJ. Decoding the mechanisms of gait generation in salamanders by combining neurobiology, modeling and robotics. BIOLOGICAL CYBERNETICS 2013; 107:545-564. [PMID: 23430277 DOI: 10.1007/s00422-012-0543-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 12/13/2012] [Indexed: 06/01/2023]
Abstract
Vertebrate animals exhibit impressive locomotor skills. These locomotor skills are due to the complex interactions between the environment, the musculo-skeletal system and the central nervous system, in particular the spinal locomotor circuits. We are interested in decoding these interactions in the salamander, a key animal from an evolutionary point of view. It exhibits both swimming and stepping gaits and is faced with the problem of producing efficient propulsive forces using the same musculo-skeletal system in two environments with significant physical differences in density, viscosity and gravitational load. Yet its nervous system remains comparatively simple. Our approach is based on a combination of neurophysiological experiments, numerical modeling at different levels of abstraction, and robotic validation using an amphibious salamander-like robot. This article reviews the current state of our knowledge on salamander locomotion control, and presents how our approach has allowed us to obtain a first conceptual model of the salamander spinal locomotor networks. The model suggests that the salamander locomotor circuit can be seen as a lamprey-like circuit controlling axial movements of the trunk and tail, extended by specialized oscillatory centers controlling limb movements. The interplay between the two types of circuits determines the mode of locomotion under the influence of sensory feedback and descending drive, with stepping gaits at low drive, and swimming at high drive.
Collapse
Affiliation(s)
- Andrej Bicanski
- Biorobotics Laboratory, School of Engineering, École Polytechnique Fédérale de Lausanne, Station 14, 1015 , Lausanne, Vaud, Switzerland,
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Initiation of segmental locomotor-like activities by stimulation of ventrolateral funiculus in the neonatal rat. Exp Brain Res 2011; 214:151-61. [PMID: 21858680 DOI: 10.1007/s00221-011-2816-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Accepted: 07/23/2011] [Indexed: 10/17/2022]
Abstract
Descending control is critically important for the generation of locomotor activities. Yet, our understanding of the descending control system of locomotion is limited. We hypothesized that stimulation of the ventrolateral funiculus (VLF) induces rhythmic activity in lumbar neurons that is correlated with locomotor-like activity in the neonatal rat. Intracellular recordings were conducted in the L2-L3 lumbar segments, while locomotor-like output was monitored in the L2 and L5 ventral roots. Stimulation of the VLF at thoracic segments induced locomotor-like activity in the L2 and L5 ventral roots in majority of the preparations (26/33). In a few midline split cord preparations (4/13), VLF stimulation induced rhythmic locomotor-like bursts in either L2 or L5 ventral root without alternating pattern between the ventral roots. The response latencies suggest that VLF stimulation induced antidromic activation (<1 ms, 8 cells), monosynaptic activation (1-3 ms, 18 cells), and oligosynaptic activation (3.5-5 ms, 14 cells) of segmental neurons in the lumbar region. VLF stimulation induced rhythmic membrane potential oscillations with or without bursting of action potentials in 9 of 40 putative interneurons. The membrane potential oscillations were in phase with the locomotor-like output of the L2 ventral root in 7 of the 9 cells while the other 2 cells oscillated in phase with the L5 ventral root activity. We have thus demonstrated that descending axons exist in the VLF which make synaptic connections with segmental neurons in the lumbar region that may be a critical element of the locomotor neural network for the initiation of locomotion.
Collapse
|
10
|
Ryczko D, Charrier V, Ijspeert A, Cabelguen JM. Segmental oscillators in axial motor circuits of the salamander: distribution and bursting mechanisms. J Neurophysiol 2010; 104:2677-92. [PMID: 20810687 DOI: 10.1152/jn.00479.2010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The rhythmic and coordinated activation of axial muscles that underlie trunk movements during locomotion are generated by specialized networks in the spinal cord. The operation of these networks has been extensively investigated in limbless swimming vertebrates. But little is known about the architecture and functioning of the axial locomotor networks in limbed vertebrates. We investigated the rhythm-generating capacity of the axial segmental networks in the salamander (Pleurodeles waltlii). We recorded ventral root activity from hemisegments and segments that were surgically isolated from the mid-trunk cord and chemically activated with bath-applied N-methyl-d-aspartate (NMDA). We provide evidence that the rhythmogenic capacity of the axial network is distributed along the mid-trunk spinal cord without an excitability gradient. We demonstrate that the burst generation in a hemisegment depends on glutamatergic excitatory interactions. Reciprocal glycinergic inhibition between opposite hemisegments ensures left-right alternation and lowers the rhythm frequency in segments. Our results further suggest that persistent sodium current contributes to the rhythmic regenerating process both in hemisegments and segments. Burst termination in hemisegments is not achieved through the activation of apamine-sensitive Ca(2+)-activated K(+) channels and burst termination in segments relies on crossed glycinergic inhibition. Together our results indicate that the basic design of the salamander axial network is similar to most of axial networks investigated in other vertebrates, albeit with some significant differences in the cellular mechanism that underlies segmental bursting. This finding supports the view of a phylogenetic conservation of basic building blocks of the axial locomotor network among the vertebrates.
Collapse
Affiliation(s)
- Dimitri Ryczko
- Pathophysiology of Spinal Networks, Neurocentre Magendie, Institut National de la Santé et de la Recherche Médicale U 862, Bordeaux University, Bordeaux Cedex, France
| | | | | | | |
Collapse
|
11
|
Ryczko D, Dubuc R, Cabelguen JM. Rhythmogenesis in axial locomotor networks: an interspecies comparison. PROGRESS IN BRAIN RESEARCH 2010; 187:189-211. [PMID: 21111209 DOI: 10.1016/b978-0-444-53613-6.00013-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
During locomotion, specialized neural networks referred to as "central pattern generators" ensure precise temporal relations between the axial segments, both in limbed and limbless vertebrates. These neural networks are intrinsically capable of generating coordinated patterns of rhythmic activity in the absence of sensory feedback or descending command from higher brain centers. Rhythmogenesis in these neural circuits lies on several mechanisms, both at the cellular and the network levels. In this chapter, we compare the anatomical organization of the axial networks, the role of identified spinal neurons, and their interactions in rhythmogenesis in four species: lamprey, zebrafish, Xenopus tadpole, and salamander. The comparison suggests that several principles in axial network design are phylogenetically conserved among vertebrates.
Collapse
Affiliation(s)
- Dimitri Ryczko
- Groupe de Recherche sur le Système Nerveux Central, Département de Physiologie, Université de Montréal, Montréal, Québec, Canada
| | | | | |
Collapse
|
12
|
Lavrov I, Cheng J. Methodological optimization of applying neuroactive agents for the study of locomotor-like activity in the mudpuppies (Necturus maculatus). J Neurosci Methods 2008; 174:97-102. [PMID: 18692523 DOI: 10.1016/j.jneumeth.2008.07.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 07/07/2008] [Accepted: 07/15/2008] [Indexed: 10/21/2022]
Abstract
We compared the effects of mode of delivery of neuroactive agents and the effects of dimethyl sulfoxide (DMSO), a vehicle for dissolving neuroactive agents, on locomotor-like activity in vitro. By superfusion, d-glutamate (0.3-0.9 mM) produced robust walking-like activity at superfusion rates 10-25 ml/min. In contrast, bolus application of the same or higher doses of glutamate (0.1-1.5 mM) failed to induce any rhythmic activity. Superfusion with AP-5, a NMDA receptor antagonist, produced dose-dependent inhibition of the ongoing walking-like activity induced by D-glutamate and completely blocked the activity at 20 microM. In contrast, bolus application of AP-5 did not block the walking-like activity at concentrations up to 120 microM. Similarly, superfusion of AP-5 inhibited the initiation of walking-like activity and completely blocked the initiation at 20 microM, while bolus application of AP-5 failed to do so at concentrations up to 120 microM. Superfusion of strychnine, a glycine receptor antagonist, blocked the walking-like activity at concentrations of 3-5 microM, while its bolus application altered NMDA-induced, but not glutamate-induced, walking-like activity to a synchronized pattern. DMSO significantly affected the walking-like activity in a dose-dependent manner at concentrations ranging 1-10% (v/v). These results demonstrate that the way by which the neuroactive agents are applied is a significant factor that determines the outcome of experiments on the neural control of locomotion. Also, the dose-dependent effects of DMSO on the activity of neural networks for locomotion should be taken into account in data interpretation.
Collapse
Affiliation(s)
- Igor Lavrov
- Department of Physiological Science and Brain Research Institute, University of California, Los Angeles, CA 90095, USA
| | | |
Collapse
|