The effects of putative non-adrenergic, non-cholinergic autonomic transmitters on isolated strips from the stomach of the rainbow trout. Salmo gairdneri.

1. The effects of some putative non-adrenergic, non-cholinergic transmitters have been studied on longitudinal and circular smooth muscle from the stomach of the rainbow trout, Salmo gairdneri. 2. ATP, adenosine and vasoactive intestinal polypeptide (VIP) on certain occasions inhibited the activity of the stomach smooth muscle; ATP and adenosine only circular muscle. VIP both longitudinal and circular muscle. 3. Neurotensin produced a contraction, which in strips from the cardiac stomach in most cases occurred after the exposure to the peptide; this might be a rebound contraction after an inhibition which could not be recorded with the experimental set-up. 4. Bombesin, 5-hydroxytryptamine and substance P produced dose-dependent contractions over a wide dose range. Somatostatin and enkephalin contracted the preparations only in the highest doses tested (10(-9) moles, 10(-8) moles). 5. Atropine did not reduce or abolish the response to any of the substances tested, indicating that their effects are not via cholinergic neurons, which innervate the smooth muscle. 6. Of the substances tested ATP, adenosine, VIP and neurotensin may be involved in the inhibitory vagal non-adrenergic, non-cholinergic innervation of the rainbow trout stomach.