Characterization of Cholinergic Control of Vasopressin Release by the Organ-cultured Rat Hypothalamo-neurohypophyseal System

Acetylcholine and nicotine stimulated vasopressin (VP) release from the organ-cultured rat hypothalamo-neurohypophyseal system (HNS). Nicotinic antagonists, hexamethonium, tetraethylammonium chloride, and trimethaphan blocked VP release in response to acetylcholine and nicotine. A muscarinic agonist, methacholine, was ineffective in eliciting VP release from HNS explants at a molar concentration equal to the maximally effective concentration of acetylcholine (10(-5) M). Atropine, a muscarinic antagonist, was an ineffective blocking agent for acetylcholine. These data indicate that the cholinergic receptor in the HNS explant is nicotinic rather than muscarinic in character.