[Identification of the nicotinic and muscarinic cholinoreceptors of the soma of the RPa4 neuron in the edible snail]

Abstract

Intracellular recording of potentials was employed to identify cholinoreceptors of the somatic membrane in Helix lucorum RPa4 neuron. A local application under pressure of specific agonists of nicotinic (nicotine, cytisine) and muscarinic (muscarine, arecoline) cholinoreceptors to the soma produced cell depolarization. Depolarization to acetylcholine application was short and was often followed by hyperpolarization. Selective desensitization of receptors by nicotine and muscarine as well as occupation of receptors by cytisine and arecoline reduced depolarization in response to acetylcholine. Nicotinic cholinergic blocker, d-tubocurarine, inhibited to a greater extent responses to nicotinic cholinomimetics, while atropine, muscarinic cholinergic blocker, inhibited responses to muscarinic cholinomimetics. Acetylcholine exhibited a mixed cholinomimetic effect: acetylcholine-induced responses were almost equally inhibited by d-tubocurarine and atropine. A hypothesis is suggested that somatic membrane of RPa4 neuron contains classical nicotinic and muscarinic acetylcholine receptors similar to those of the vertebrates.