Analysis of relaxant effects of trapidil in isolated dog coronary artery

Effects of 7-diethylamino-5-methyl-s-triazolo [1,5-a]pyrimidine (trapidil, Rocornal) on dog coronary arteries were investigated in vitro. Trapidil produced dose-dependent relaxations of isolated arteries which were contracted with potassium or prostaglandins F2 alpha. These effects of trapidil were not affected by atropine and propranolol. 5-Hydroxytryptamine (5-HT) and phenylephrine dose-dependently increased the tension of isolated coronary arteries. Trapidil could inhibit these effects of 5-HT or phenylephrine. The results indicate that trapidil has not a muscarinic action and an adrenergic beta-receptor stimulating action, but it has a 5-HT receptor and an adrenergic alpha-receptor blocking action.