[Effect of activation of the cholinergic system of the small intestine on its contractile responses induced by serotonin].

In acute experiments on cats, an isolated portion of the small intestine was vascularly perfused with arterial blood by means of the constant volume perfusion pump. Contractile activity of the ileal and/or jejunal segment was estimated by means of isometric tension. Activation of the myenteric cholinergic neurons as the result of the infusion of nicotinic cholinoreceptor agonist subecholine or electrical stimulation of the vagal efferents was followed by increased contractile response of intestinal smooth muscle to serotonin (2.5 X 10(-8) or 5.0 X 10(-9) mol). The same effect was observed after increasing endogenous acetylcholine concentration induced with application of anticholinesterase drug prozerin. The data obtained suggested that the modulating effect of acetylcholine might be of a certain physiological importance.