Effects of ganglionic blockade and voluntary muscle paralysis on epinephrine blood pressure responses

¹ Department of Pharmacology, University of Mississippi Medical Center, Jackson, Mississippi

The blood pressure responses elicited by graded doses of epinephrine before and after voluntary muscle paralysis by curare have been studied in the dog anesthetized with sodium pentobarbital and pretreated with diphenhydramine and hexamethonium. These responses were compared before and after curare to determine the effects of voluntary muscle paralysis. The results were also compared with the earlier results of Hilton and Reid (Am. J. Physiol. 186: 289, 1956) obtained in dogs under total spinal anesthesia. The comparisons showed that the actual rise in blood pressure and the duration of the rise in blood pressure were unaffected by the paralysis of the voluntary muscle. The maximum attainable blood pressure was lower following the curare. The amount of lowering in maximum was directly related to the effects of the curare upon the control blood pressure. The comparison of the blood pressure responses to epinephrine after diphenhydramine and hexamethonium with the blood pressure responses obtained from the same doses of epinephrine in unmedicated dogs showed that the diphenhydramine-hexamethonium potentiated the pressor responses. When the same comparison was made with responses in the dog under total spinal anesthesia there was no potentiation of the pressor responses. The results of these experiments seem to indicate that the potentiation of epinephrine pressor response varies with the degree of autonomic nervous activity, but not with voluntary muscle activity.