A Pharmacological Study of Intestinal Vasodilator Mechanisms in the Cat

Abstract

Abstract The intestinal vasodilator responses evoked by close i.a. administration of cholecystokinin (CCK) and secretin, mechanical stimulation of the mucosa and transmural electrical field stimulation were abolished by the 5‐hydroxytryptamine (5‐HT) antagonist dihydroergotamine, given in doses sufficient to block the vascular effects of i.a. injected 5‐HT. Corresponding results were obtained by making the cat small intestine tachyphylactic to 5‐HT. Nervous blockade (tetrodotoxin), inhibiting the intestinal blood flow increase after mechanical mucosal or electrical field stimulation, left the vascular responses to exogenous CCK and secretin unaffected. An increased 5‐HT content in venous blood from the intestine was demonstrated during vasodilatations caused by electrical field stimulation. A participation of intestinal 5‐HT, possibly as a transmitter substance, in the vasodilator mechanism evoked by mechanical mucosal stimulation or electrical transmural field stimulation is suggested.