The action of cholinergic antagonists on the effect of acetylcholine, nicotine and benzoylcholine applied iontophoretically onto two identified neurones in the brain of helix aspersa

Abstract

1. Intracellular recordings were made from 2 identified neurones in the brain of Helix aspersa. Cell E4 is inhibited by acetylcholine while cell F1 is excited by acetylcholine. 2. Thirteen cholinolytic agents were tested for their blocking actions against iontophoretically-applied acetylcholine on the 2 cells. The compounds examined were strychnine, scopolamine, atropine, tubocurarine, pancuronium, gallamine, hexamethonium, pentolinium, mecamylamine, benzoquinonium, decamethonium, suxamethonium and benzolcholine. All the compounds were at least partial antagonists on cell E4 while only three, i.e. scopolamine, decamethonium and suxamethonium, did not block the cholinergic receptors of cell F1. 3. Four cholinolytics were further tested as antagonists against iontophoretically-applied nicotine and benzoylcholine; these were atropine, strychnine, tubocurarine and hexamethonium. The only compound which did not block the actions of nicotine and benzoylcholine on both cells was strychnine which had no blocking action against benzoylcholine on cell F1.