Arterial Pressure Response to Infused Serotonin in Normotensive Dogs, Cats, Hypertensive Dogs and Man

Abstract

Arterial pressure response to intravenous infusion of serotonin in dogs and cats is usually a sustained fall; this differs from the usual response to a single quick injection of serotonin and suggests that the mechanisms controlling response are different depending upon the manner of administration of the drug. It is concluded that when serotonin is infused the depressor response has at least three main contributory mechanisms: a) release of endogenous histamine by serotonin; b) peripheral inhibition of neurogenic vasoconstriction; c) a dose-response relationship that, in some preparations, determines whether change in arterial pressure shall be a rise or fall. The response to intravenous infusion of serotonin in three hypertensive patients was different from that in normotensive dogs and cats or neurogenic hypertensive dogs. These patients responded with a small, sustained rise in arterial pressure. Infusion of either histamine or serotonin in dogs caused similar changes in response to other drugs: those to DMPP were strikingly augmented and those to noradrenaline were moderately increased in both dogs and cats. Responses to angiotonin, barium chloride, and Aramine were essentially unchanged. The depressor action of the histamine releasing drug, 48/80, or histamine, was sharply reduced or abolished.