Control of the Splanchnic Circulation in Man

Abstract

Some effects of the [beta]-adrenergic receptor blocker, propranolol, were studied in 20 normal, fasting, conscious men. The measurements made included cardiac output, splanchnic blood flow and oxygen consumption, arterial and hepatic venous blood pressure, and heat rate. The intravenous administration of propranolol (0.13 mg/kg) was followed by significant reductions in splanchnic blood flow and oxygen consumption, in cardiac output and in heart rate. Splanchnic perfusion pressure was unchanged; the splanchnic vascular resistance was significantly elevated. Previous treatment with glucose did not alter these findings. Phenoxybenzamine pretreatment lessened the increase in splanchnic vascular resistance which propranolol ordinarily caused. Ganglionic blockade with hexamethonium prevented all of the changes which propranolol produced in untreated individuals. These results may best be explained by assuming that the splanchnic circulation in man is influenced both by a receptors, which cause vasoconstriction when activated, and by B receptors, which when activated cause vaso-dilatation and increase oxygen consumption.