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Cholinergic control of excitability of spinal motoneurones in the salamander
Author(s) -
Chevallier Stéphanie,
Nagy Frédéric,
Cabelguen JeanMarie
Publication year - 2006
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2005.098970
Subject(s) - muscarine , muscarinic acetylcholine receptor , chemistry , afterhyperpolarization , depolarization , acetylcholine , neuroscience , cholinergic , hyperpolarization (physics) , membrane potential , reversal potential , carbachol , endocrinology , electrophysiology , medicine , patch clamp , receptor , biology , biochemistry , organic chemistry , nuclear magnetic resonance spectroscopy
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 μ m ) with eserine (20 μ m ) 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 μ m ), and blocked by application of the muscarinic receptor antagonist atropine (0.1–1 μ m ). They were not observed during bath application of nicotine (10 μ m ). 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.