Alteration of vascular responses to endotoxin by adrenergic blockade

Abstract

The effects of the adrenergic blocking agent phenoxybenzamine (Dibenzyline) on the vascular responses to injected histamine and endotoxin were studied in dogs utilizing a "venous return" preparation. A marked antihistaminic action of Dibenzyline was demonstrated in the hepatic portal system. Less effective blocking was seen in the arterial segment. The effectiveness of Dibenzyline for preventing increases in portal venous pressure and pooling of blood were similar with both histamine and endotoxin administration. These data show a basic similarity between the early vascular responses to histamine and endotoxin in the hepatic-portal system. A major dissimilarity between the vascular effects of histamine and endotoxin was the absence of an early drop in total peripheral resistance after endotoxin. Beneficial effects of Dibenzyline after endotoxin, during the first 100 min, could not be demonstrated in animals whose cardiac output was unsupported. The action of Dibenzyline alone is apparently incapable of reversing the detrimental effects of endotoxin.