Early Potentiation of the Vasoconstrictor Action of Norepinephrine by Guanethidine.

Abstract

The effects of norepinephrine on blood flow and vascular tone were determined before and immediately after intravenous guanethidine in healthy men and intact dogs. The pressor effect of norephrine was enhanced by guanethidine. In dogs, this resulted from augmentation of the vasoconstrictor action of norephinephrine rather than from higher blood flow. In humans, it was the result of both increased vascular tone and higher flow. The mechanism of this type of hypersen-sitivity is obscure. Guanethidine may have a direct action on receptors which increases their sensitivity to norepinephrine.