Papers by Stephanie Chevallier
Neuroscience Bulletin, Jul 28, 2013
Recovery of locomotor behavior following spinal cord injury can occur spontaneously in some verte... more Recovery of locomotor behavior following spinal cord injury can occur spontaneously in some vertebrates, such as fish, urodele amphibians, and certain reptiles. This review provides an overview of the current status of our knowledge on the anatomical and electrophysiological changes occurring within the spinal cord that lead to, or are associated with the re-expression of locomotion in spinally-transected salamanders. A better understanding of these processes will help to devise strategies for restoring locomotor function in mammals, including humans.
European Journal of Neuroscience, Oct 1, 2004
Electromyographic (EMG) analysis was used to provide an assessment of the recovery of locomotion ... more Electromyographic (EMG) analysis was used to provide an assessment of the recovery of locomotion in spinal-transected adult salamanders (Pleurodeles waltlii). EMG recordings were performed during swimming and overground stepping in the same animal before and at various times (up to 500 days) after a mid-trunk spinalization. Two-three weeks after spinalization, locomotor EMG activity was limited to the forelimbs and the body rostral to the transection. Thereafter, there was a return of the locomotor EMG activity at progressively more caudal levels below the transection. The animals reached stable locomotor patterns 3-4 months post-transection. Several locomotor parameters (cycle duration, burst duration, burst proportion, intersegmental phase lag, interlimb coupling) measured at various recovery times after spinalization were compared with those in intact animals. These comparisons revealed transient and long-term alterations in the locomotor parameters both above and below the transection site. These alterations were much more pronounced for swimming than for stepping and revealed differences in adaptive plasticity between the two locomotor networks. Recovered locomotor activity was immediately abolished by retransection at the site of the original spinalization, suggesting that the spinal cord caudal to the transection was reinnervated by descending brain and/or propriospinal axons, and that this regeneration contributed to the restoration of locomotor activity. Anatomical studies conducted in parallel further demonstrated that some of the regenerated axons came from glutamatergic and serotoninergic immunoreactive cells within the reticular formation.
The Journal of Physiology, Jan 16, 2006
The cholinergic modulation of the electrical properties of spinal motoneurones was investigated i... more The cholinergic modulation of the electrical properties of spinal motoneurones was investigated in vitro, with the use of the whole-cell patch-clamp recording technique in lumbar spinal cord slices from juvenile urodeles (Pleurodeles waltlii). Bath application of acetylcholine (20 μm) with eserine (20 μm) induced an increase in the resting membrane potential, a decrease of the input resistance, a decrease of the action potential amplitude, and a reduction of the medium afterhyperpolarization (mAHP) that followed each action potential. Moreover, the firing rate of motoneurones during a depolarizing current pulse and the slope of their stimulus current–spike frequency relation were increased. All of these effects were mimicked by extracellular application of muscarine (20 μm), and blocked by application of the muscarinic receptor antagonist atropine (0.1–1 μm). They were not observed during bath application of nicotine (10 μm). These results suggest that the cholinergic modulation of spinal motoneurone excitability was mediated by activation of muscarinic receptors. Our results further show that the muscarinic action primarily resulted from a reduction of the Ca2+-activated K+ current responsible for the mAHP, an inhibition of the hyperpolarization-activated cation current, Ih, and an enhancement of the inward rectifying K+ current, IKir. We conclude that cholinergic modulation can contribute significantly to the production of motor behaviour by altering several ionic conductances responsible for the repetitive discharge of motoneurones.
Journal of Neuroscience, 2008
Proceedings of the National Academy of Sciences, 2011
When animals move, respiration increases to adapt for increased energy demands; the underlying me... more When animals move, respiration increases to adapt for increased energy demands; the underlying mechanisms are still not understood. We investigated the neural substrates underlying the respiratory changes in relation to movement in lampreys. We showed that respiration increases following stimulation of the mesencephalic locomotor region (MLR) in an in vitro isolated preparation, an effect that persists in the absence of the spinal cord and caudal brainstem. By using electrophysiological and anatomical techniques, including whole-cell patch recordings, we identified a subset of neurons located in the dorsal MLR that send direct inputs to neurons in the respiratory generator. In semi-intact preparations, blockade of this region with 6-cyano-7-nitroquinoxaline-2,3-dione and (2R)-amino-5-phosphonovaleric acid greatly reduced the respiratory increases without affecting the locomotor movements. These results show that neurons in the respiratory generator receive direct glutamatergic conne...
Cellular Signalling, 2011
The Journal of Physiology, 2006
The cholinergic modulation of the electrical properties of spinal motoneurones was investigated i... more The cholinergic modulation of the electrical properties of spinal motoneurones was investigated in vitro, with the use of the whole-cell patch-clamp recording technique in lumbar spinal cord slices from juvenile urodeles (Pleurodeles waltlii). Bath application of acetylcholine (20 µM) with eserine (20 µM) induced an increase in the resting membrane potential, a decrease of the input resistance, a decrease of the action potential amplitude, and a reduction of the medium afterhyperpolarization (mAHP) that followed each action potential. Moreover, the firing rate of motoneurones during a depolarizing current pulse and the slope of their stimulus current-spike frequency relation were increased. All of these effects were mimicked by extracellular application of muscarine (20 µM), and blocked by application of the muscarinic receptor antagonist atropine (0.1-1 µM). They were not observed during bath application of nicotine (10 µM). These results suggest that the cholinergic modulation of spinal motoneurone excitability was mediated by activation of muscarinic receptors. Our results further show that the muscarinic action primarily resulted from a reduction of the Ca 2+-activated K + current responsible for the mAHP, an inhibition of the hyperpolarization-activated cation current, I h , and an enhancement of the inward rectifying K + current, I Kir. We conclude that cholinergic modulation can contribute significantly to the production of motor behaviour by altering several ionic conductances responsible for the repetitive discharge of motoneurones.
Neuroscience Bulletin, 2013
European Journal of Neuroscience, 2004
Electromyographic (EMG) analysis was used to provide an assessment of the recovery of locomotion ... more Electromyographic (EMG) analysis was used to provide an assessment of the recovery of locomotion in spinal-transected adult salamanders (Pleurodeles waltlii). EMG recordings were performed during swimming and overground stepping in the same animal before and at various times (up to 500 days) after a mid-trunk spinalization. Two-three weeks after spinalization, locomotor EMG activity was limited to the forelimbs and the body rostral to the transection. Thereafter, there was a return of the locomotor EMG activity at progressively more caudal levels below the transection. The animals reached stable locomotor patterns 3-4 months post-transection. Several locomotor parameters (cycle duration, burst duration, burst proportion, intersegmental phase lag, interlimb coupling) measured at various recovery times after spinalization were compared with those in intact animals. These comparisons revealed transient and long-term alterations in the locomotor parameters both above and below the transection site. These alterations were much more pronounced for swimming than for stepping and revealed differences in adaptive plasticity between the two locomotor networks. Recovered locomotor activity was immediately abolished by retransection at the site of the original spinalization, suggesting that the spinal cord caudal to the transection was reinnervated by descending brain and/or propriospinal axons, and that this regeneration contributed to the restoration of locomotor activity. Anatomical studies conducted in parallel further demonstrated that some of the regenerated axons came from glutamatergic and serotoninergic immunoreactive cells within the reticular formation.
Brain Research Reviews, 2008
European Journal of Neuroscience, 2008
The excitability of spinal motoneurons (MNs) is regulated by acetylcholine via the activation of ... more The excitability of spinal motoneurons (MNs) is regulated by acetylcholine via the activation of muscarinic receptors. The objective of the present study was to determine whether this cholinergic modulation of MN excitability is altered following a chronic spinal cord transection. Juvenile salamanders (Pleurodeles waltlii) were spinally transected at the mid-trunk level, and patch-clamp recordings from hindlimb MNs in spinal cord slices were performed 9-30 days after transection, with and without bath application of muscarine (20 mum). Our results showed that the input-output relationship was larger in MNs recorded 2 weeks after spinal transection than in MNs recorded 3-4 weeks after spinal transection. They further revealed that muscarine increased both the gain of MNs and the proportion of MNs that could exhibit plateau potentials and afterdischarges, whereas it decreased the amplitude of the medium afterhypolarizing potential. Moreover, muscarine had no effect on the hyperpolarization-activated cation current (I(h)), whereas it increased the inward rectifying K(+) current (I(Kir)) in MNs recorded > or = 2 weeks after spinal transection. We conclude that following chronic spinal cord injury, the muscarinic modulation of some intrinsic properties of MNs previously reported in acute spinal-transected animals [S. Chevallier et al. (2006)The Journal of Physiology, 570, 525-540] was preserved, whereas that of other intrinsic properties of MNs was suppressed, either transiently (I(Kir)) or definitively (I(h)). These alterations in muscarinic modulation of MN excitability may contribute to the spontaneous recovery of locomotion displayed in long-term chronic spinal-transected salamanders.
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Papers by Stephanie Chevallier