THE BLOCKADE OF THE PRESSOR RESPONSE TO TYRAMINE BY AMPHETAMINE IN THE RESERPINE-TREATED DOG

¹ Department of Pharmacology, Pitman-Moore Division of The Dow Chemical Company, Zionsville, Indiana

In the anesthetized dog, the acute administration of either reserpine or amphetamine increases the pressor response to tyramine. This was found for both systemic arterial blood pressure response to intravenous tyramine and the perfusion pressure response in the perfused hind limb to intraarterial tyramine in the case of reserpine, but only for the systemic arterial blood pressure in the case of amphetamine. When amphetamine and reserpine were both given, in either order, the pressor responses to tyramine were diminished. The pressor responses remaining in a dog pretreated with reserpine for 18 to 24 hr were also antagonized by the acute administration of amphetamine. The antagonism of the pressor responses to tyramine by combinations of amphetamine and reserpine in the acute experiments cannot yet be explained. The finding that the response of the perfused leg to intraarterial tyramine was potentiated, in the period immediately following the administration of reserpine, suggests a peripheral rather than a central mechanism for this action of reserpine.