Metachronal coupling between spinal neuronal networks during locomotor activity in newborn rat.
The Journal of Physiology. 2007-03-21; 580(1): 87-102
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1. J Physiol. 2007 Apr 1;580(Pt 1):87-102. Epub 2006 Dec 21.
Metachronal coupling between spinal neuronal networks during locomotor activity
in newborn rat.
Falgairolle M(1), Cazalets JR.
(1)CNRS Unité Mixte de Recherche 5227, Université Bordeaux 2, Zone nord Bat 2,
146, rue Léo Saignat, 33076 Bordeaux Cedex, France.
In the present study, we investigate spinal cord neuronal network interactions in
the neonatal rat during locomotion. The behavioural and physiological relevance
of metachronally propagated locomotor activity were inferred from kinematic,
anatomical and in vitro electrophysiological data. Kinematic analysis of freely
behaving animals indicated that there is a rhythmic sequential change in trunk
curvature during the step cycle. The motoneurons innervating back and tail
muscles were identified along the spinal cord using retrograde labelling.
Systematic multiple recordings from ventral roots were made to determine the
precise intrinsic pattern of coordination in the isolated spinal cord. During
locomotor-like activity, rhythmic ventral root motor bursts propagate
caudo-rostrally in the sacral and the thoracic spinal cord regions. Plotting the
latency as a function of the cycle period revealed that the system adapts the
intersegmental latency to the ongoing motor period in order to maintain a
constant phase relationship along the spinal axis. The thoracic, lumbar and
sacral regions were capable of generating right and left alternating motor bursts
when isolated. Longitudinal sections of the spinal cord revealed that both the
bilateral antiphase pattern observed for the sacral region with respect to the
lumbar segment 2 as well as the intersegmental phase lag were due to cross-cord
connections. Together, these results provide physiological evidence that the
dynamic changes observed in trunk bending during locomotion are determined by the
intrinsic organization of spinal cord networks and their longitudinal and
transverse interactions. Similarities between this organization, and that of
locomotor pattern generation in more primitive vertebrates, suggest that the
circuits responsible for metachronal propagation of motor patterns during
locomotion are highly conserved.
PMID: 17185345 [Indexed for MEDLINE]