A CALCIUM‐DEPENDENT ACETYLCHOLINE DEPOLARIZATION BLOCKED BY METHOXYVERAPAMIL (D600) AND PROCAINE IN SNAIL NEURONES

Abstract

1 Repetitive application of acetylcholine (ACh) revealed two types of ACh depolarization in two types of snail neurone, depending on their desensitization properties. 2 Further experiments were carried out on neurones which displayed a rapidly desensitizing response. 3 The amplitude of the response depended on the external sodium and calcium levels. 4 Procaine antagonized ACh effects with the same efficiency as atropine or hexamethonium, half maximal depression being obtained at a concentration of 10⁻⁴m. The blocking effect was independent of the dose of ACh. 5 The depression of the ACh-induced depolarization by cobalt ions and D600 suggests that calcium may participate in this response.