Abstract

A variety of different drugs and conditions which alter either a portion of or all of the sympathetic tone of the dog have been studied to determine their influence upon the pressor responses elicited by intravenous epinephrine. The results of these studies have shown: (1) Removal of the adrenal either by surgical means or by drug action using P-286 does not alter the epinephrine pressor response. (2) Interruption of only the sympathetic nerves by use of bretylium produces a slight increase of pressor response which is not statistically significant. (3) Interruption of both the adrenal and the sympathetic nerves by ganglionic blockade with hexamethonium, surgical sympathoadrenalectomy or total spinal anesthesia potentiates the epinephrine pressor response to a significant degree. (4) Depletion of catecholamines or blockade of their release by reserpine or guanethidine also potentiates the epinephrine pressor response. From these results it has been postulated that for significant potentiation of the epinephrine pressor response to occur both the adrenal secretion and the activity of the sympathetic nerves must be blocked.