NICOTINIC AND MUSCARINIC ACETYLCHOLINE RESPONSES IN THE EMBRYO CHICK CILIARY GANGLION-CELLS

Nicotinic and muscarinic acetylcholine (ACh) responses were investigat ed in acutely dissociated chick ciliary ganglion neurons using the nys tatin perforated patch clamp technique. ACh-induced a rapid transient inward current in 100% of the neurons at a holding potential of -60 mV . This rapid inward current was mimicked by nicotine but not by muscar ine. The reversal potential of the rapid inward current was + 10.5 mV and the current was inhibited by d-tubocurarine and hexamethonium in a dose-dependent manner. In 57.6% of neurons, a slow inward current was also induced by ACh at a holding potential of -20 mV. This slow inwar d current was mimicked by muscarine but not by nicotine. The slow inwa rd current became smaller at a hyperpolarized potential but not revers ed, being consistent with the fact that this current was elicited by t he inhibition of M-current. p-Fluorohexa-hydrosiladifenidol (P-F-HHSiD ) strongly inhibited the slow inward current, suggesting that the curr ent was elicited by the activation of M(3) receptors.