Spinal and pontine relay pathways mediating respiratory rhythm entrainment by limb proprioceptive inputs in the neonatal rat.
Journal of Neuroscience. 2012-08-22; 32(34): 11841-11853
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1. J Neurosci. 2012 Aug 22;32(34):11841-53. doi: 10.1523/JNEUROSCI.0360-12.2012.
Spinal and pontine relay pathways mediating respiratory rhythm entrainment by
limb proprioceptive inputs in the neonatal rat.
Giraudin A(1), Le Bon-Jégo M, Cabirol MJ, Simmers J, Morin D.
(1)Unité Mixte de Recherche 5287, Institut de Neurosciences Cognitives et
Intégratives d’Aquitaine, Centre National de la Recherche Scientifique,
Université Bordeaux, F-33000 Bordeaux, France.
The coordination of locomotion and respiration is widespread among mammals,
although the underlying neural mechanisms are still only partially understood. It
was previously found in neonatal rat that cyclic electrical stimulation of spinal
cervical and lumbar dorsal roots (DRs) can fully entrain (1:1 coupling)
spontaneous respiratory activity expressed by the isolated brainstem/spinal cord.
Here, we used a variety of preparations to determine the type of spinal sensory
inputs responsible for this respiratory rhythm entrainment, and to establish the
extent to which limb movement-activated feedback influences the medullary
respiratory networks via direct or relayed ascending pathways. During in vivo
overground locomotion, respiratory rhythm slowed and became coupled 1:1 with
locomotion. In hindlimb-attached semi-isolated preparations, passive
flexion-extension movements applied to a single hindlimb led to entrainment of
fictive respiratory rhythmicity recorded in phrenic motoneurons, indicating that
the recruitment of limb proprioceptive afferents could participate in the
locomotor-respiratory coupling. Furthermore, in correspondence with the
regionalization of spinal locomotor rhythm-generating circuitry, the stimulation
of DRs at different segmental levels in isolated preparations revealed that
cervical and lumbosacral proprioceptive inputs are more effective in this
entraining influence than thoracic afferent pathways. Finally, blocking spinal
synaptic transmission and using a combination of electrophysiology, calcium
imaging and specific brainstem lesioning indicated that the ascending entraining
signals from the cervical or lumbar limb afferents are transmitted across
first-order synapses, probably monosynaptic, in the spinal cord. They are then
conveyed to the brainstem respiratory centers via a brainstem pontine relay
located in the parabrachial/Kölliker-Fuse nuclear complex.
PMID: 22915125 [Indexed for MEDLINE]