Effects of ganglionic blockade by hexamethonium on blood pressure responses to histamine

¹ Department of Pharmacology, Marquette University School of Medicine, Milwaukee, Wisconsin

The effects of blockade of the autonomic ganglia by administration of hexamethonium on blood pressure responses to histamine were studied in the dog anesthetized with sodium pentobarbital. A series of graded doses of histamine acid phosphate were administered before and after the blockade of the ganglia, and blood pressure responses elicited by these doses of histamine were analyzed for minimum attained blood pressure and actual fall and duration of fall in blood pressure. In all cases the minimum attained blood pressure was lower after administration of the ganglionic blocking agent than before. The amount of lowering of the minimum attainable blood pressure was about the same as that of lowering of the control blood pressure produced by the ganglionic blocking agent. Actual fall in blood pressure was unaffected by administration of the ganglionic blocking agent but duration of the fall following all the larger doses of histamine was markedly prolonged by this same procedure. Prolongation of depressor response and lowering of minimum attained blood pressure seem to be more related to the presence or absence of autonomic nervous activity than to the level of control blood pressure.

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