Effects of dopamine and other catecholamines on the splanchnic circulation.

Abstract

Studies were conducted to evaluate the effects of dopamine (3, 4-dihydroxyphenylethylamine) and other catecholamines on the mesenteric vascular bed in dogs. Mesenteric and hepatic artery blood flows were measured with electromagnetic blood flow transducers. Catecholamines were infused intra-arterially into a branch-of the mesenteric artery. Dopamine consistently decreased mesenteric and hepatic artery blood flows at all dose levels studied (5–100 mg/kg). Phenoxybenzamine (12.5 mg/kg) blocked the effects of norepinephrine (0.05–1.0 μg/kg) and reversed the responses to dopamine in the mesenteric bed to those of pure vasodilation (no transient constriction was observed) but failed to abolish the constrictor action of dopamine on the hepatic artery. Propranolol or haloperidol, when administered with the phenoxybenzamine, did not attenuate the mesenteric responses to dopamine. Haloperidol prevented the hepatic artery vasoconstriction produced by dopamine but did not alter isoproterenol-induced hepatic artery vasodilation. No competitive action was observed between dopamine and norepinephrine or isoproterenol. These results suggest that (1) dopamine produces selective vasodilation of the mesenteric bed which is not blocked by haloperidol, and (2) dopamine has a unique action on the hepatic vascular bed which is blocked by haloperidol.