Hydroxytryptaminergic transmission in a frog vagus-stomach muscle preparation

Abstract

1. 5-hydroxytryptamine as well as vagal stimulation produce contraction and relaxation of frog stomach muscle which are abolished by 2-bromolysergic acid diethylamide, tryptamine and 5-hydroxytryptamine. It is therefore concluded that 5-hydroxytryptamine acts as a vagal transmitter. 2. Vagal stimulation of frog stomach muscle also produces adrenergic relaxation. 3. The contraction of frog stomach muscles produced by vagal stimulation shows seasonal variations in its resistance to the action of four antagonists: atropine, mepyramine, bromolysergic acid diethylamide and acetylsalicylic acid. Correspondingly the muscle shows similar variations in its sensitivity to acetylcholine, histamine, 5-hydroxytryptamine and polypeptides.