State-dependent regulation of sensory-motor transmission: role of muscarinic receptors in sensory-motor integration in the crayfish walking system.
European Journal of Neuroscience. 2006-03-01; 23(5): 1283-1300
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1. Eur J Neurosci. 2006 Mar;23(5):1283-300.
State-dependent regulation of sensory-motor transmission: role of muscarinic
receptors in sensory-motor integration in the crayfish walking system.
Le Bon-Jego M(1), Masante-Roca I, Cattaert D.
(1)Laboratoire de Neurobiologie des Réseaux, CNRS UMR 5816, Université Bordeaux
1, Biologie Animale, Talence, France.
The aim of this study was to investigate a potential mechanism for
state-dependent regulation of sensory-motor transmission from sensory afferents
of a proprioceptor to motoneurons (MNs) in the walking system of the crayfish.
This study was performed using an in vitro preparation of thoracic ganglia
including motor nerves and the proprioceptor that codes movements of the second
joint (coxo-basal chordotonal organ – CBCO) of the leg. Application of movements
to the CBCO elicits resistance reflex responses intracellularly recorded from Dep
MNs. This reflex response is enhanced when Dep MNs are depolarized either
spontaneously or by current injection. This enhancement is abolished in the
presence of scopolamine (an antagonist of muscarinic acetylcholine receptors).
Using pharmacology, we demonstrate that the monosynaptic connection from CBCO
sensory neurons to the Dep MNs includes both nicotinic and muscarinic components.
In addition, the shape of monosynaptic excitatory postsynaptic potentials (EPSPs)
depends on the membrane potential: at a subthreshold depolarizing membrane
potential, the time constant of the falling phase of the EPSPs is significantly
increased compared with its value at resting potential. This change is suppressed
in the presence of scopolamine, indicating that the muscarinic component may
contribute to the activation of the Dep MN pool by sensory activity. This
state-dependent amplification of the sensory input may be important for
increasing the strength of sensory feedback at times when central activation of
the Dep MNs is very strong (e.g. during walking).
PMID: 16553790 [Indexed for MEDLINE]