In-vitro study of the enkephalinergic hypothesis for non-adrenergic, non-cholinergic innervation in the cat stomach

It has been suggested that enkephalins are involved in the gastric relaxation induced by stimulation of the non-adrenergic, non-cholinergic vagal fibres in the cat stomach. Experiments were therefore performed on strips of cat stomach. With longitudinal and circular gastric fundus and corpus strips from reserpinized cats, non-adrenergic, non-cholinergic relaxatory responses could be elicited by transmural electrical stimulation in Tyrode solution containing atropine and 5-hydroxytryptamine. Morphine, leu-enkephalin and met-enkephalin did not influence the tone of the strips or the relaxation evoked by stimulation at 8 Hz, and neither did the opioid antagonist, naloxone. These results do not support the enkephalinergic hypothesis for the non-adrenergic, non-cholinergic vagal fibres in the cat stomach.