Forelimb locomotor generators and quadrupedal locomotion in the neonatal rat
European Journal of Neuroscience. 2001-11-01; 14(10): 1727-1738
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1. Eur J Neurosci. 2001 Nov;14(10):1727-38.
Forelimb locomotor generators and quadrupedal locomotion in the neonatal rat.
Ballion B(1), Morin D, Viala D.
(1)Laboratoire de Neurobiologie des Réseaux, Université Bordeaux I & CNRS UMR
5816, Avenue des Facultés, 33405 Talence cedex, France.
The spinal localization of the forelimb locomotor generators and their
interactions with other spinal segments were investigated on in vitro
brainstem-spinal cord preparations of new-born rats. Superfusion of the
cervicothoracic cord (C1-T4) with high K+/low Mg2+ artificial cerebrospinal fluid
(aCSF) evoked rhythmic motor root activity that was limited to low cervical (C7,
C8) and high thoracic (T1) spinal levels. This activity consisted of synchronous,
homolateral bursts and a typical alternating bilateral pattern. Rhythmic activity
with similar locomotor-like characteristics could be induced with either
serotonin (5-HT, 5 microm), N-methyl-d-aspartate (NMDA, 5 microm), kainate (10
microm) or a “cocktail” of 5-HT (5 microm) and NMDA (5 microm). During 5-HT/NMDA
perfusion of the cervicothoracic cord, induced bursting was no longer restricted
to C7-T1 levels, but also occurred at cervical C3-C5 levels and with C5-C8
homolateral alternation. Spinal transections between C6 and C7 cervical segments
did not abolish rhythmic activity in C7-T1, but suppressed locomotor-like
rhythmicity at C3-C5 levels. Reduced regions comprising the C7-C8 or C8-T1
segments maintained rhythmicity. Superfusion of the whole cord with 5-HT/NMDA
induced ventral root bursting with similar frequencies at all recorded segments
(cervical, thoracic and lumbar). After isolation, the T3-T10 cord was unable to
sustain any rhythmic activity while cervical and lumbar segmental levels
continued to burst, albeit at different frequencies. We also found that the
faster caudal and the slower rostral locomotor generators interact to produce
coordinated locomotor-like activity in all segments of the intact spinal cord. In
conclusion, C7-T1 spinal levels display a strong motor rhythmogenic ability; with
the lumbar generators, they contribute to coordinated rhythmic activity along the
entire spinal cord of a quadrupedal locomoting mammal.
PMID: 11860467 [Indexed for MEDLINE]