Evidence for peripheral cholinergic components in thirst-induced water consumption

The volume of water consumed in a 60 min period by rats deprived of water for 23 hr was significantly reduced by administration of tertiary amine cholinergic blocking agents such as atropine, homatropine or scopolamine, or by administration of their quaternary N-methyl derivatives. Dose-response curves for the tertiary amines were mutually parallel and showed a potency order of scopolamine>atropine>homatropine. Dose-response curves for the quaternary compounds were not parallel. The effect of methylatropine on thirst-induced water consumption showed a significant carryover effect on the post-drug day. Reduction of thirst-induced drinking could also be achieved by administration of acetylcholinesterase inhibitors such as physostigmine and neostigmine. The results presented infer the presence of a peripheral cholinergic component in thirst-induced water consumption.