AN EVALUATION OF THE VASODILATION PRODUCED BY MEPHENTERMINE AND CERTAIN OTHER SYMPATHOMIMETIC AMINES

¹ Department of Pharmacology and the Department of Medicine (Division of Clinical Pharmacology), Emory University, Atlanta, Georgia

Mephentermine injected into femoral, renal or superior mesenteric arteries of pentobarbital-anesthetized dogs increased blood flow in proportion to dose. The effect was not blocked by propranolol, atropine or antihistamine compounds. Vasodilation was also observed with pseudoephedrine, d-amphetamine, methamphetamine, methyiphenidate, Lilly 390 and BW 654. No apparent relationship between structure and vasodilating activity was noted among these amines. Each of these amines also produced secondary vasoconstriction, particularly after phenoxybenzamine or reserpine. Segmental resistance studies in the perfused forelimb of phenoxybenzamine-pretreated dogs showed that the decrease in total resistance produced by mephentermine is due to a reduction in small vessel resistance, as is the case with isoproterenol and glyceryl trinitrate. Mephentermine, unlike the other agents, increased resistance in the arterial segment. Isolated rabbit portal veins showed a dose-related relaxation to mephentermine which was not blocked by MJ-1999 in a dose which blocked the effects of isoproterenol. The demonstration of this vasodilation in these three vascular beds and relaxation of the isolated portal vein suggests that this dilating phenomenon is not selective as to vascular bed.