Hemodynimic effects of systemic and central administration of clonidine in the monkey

Abstract

Systemic and regional hemodynamic changes were measured in restrained, conscious rhesus monkeys with indwelling arterial and venous catheters before and after clonidine (5 and 15 mug/kg) was slowly infused intravenously or smaller doses (2 mug/kg) were injected into a lateral cerebral ventricle. Dye-dilution cardiac outputs and the complete distribution of cardiac output were obtained intermittently with the use of the radioactive microsphere method. After the higher intravenous dose and the intraventricular injection, systemic arterial pressure was significantly lowered for 30-45 min. Both of these groups had similar changes in the redistribution of cardiac output and blood flow that outlasted the hypotensive period. Blood flow was maintained or increased in the hepatic and renal arteries at the expense of skin; flow to skeletal muscle and brain also decreased during the first hour. These data support previous studies that indicate that the primary action of clonidine is in the central nervous system and, in addition, add new information about the regional blood flow changes evoked by clonidine.

The Pharmacology of Clonidine and Related Products

“…(1974) did not find a decrease in splanchnic blood flow in rats. Hepatic blood flow has been found to be increased in monkeys after intravenous or intracerebroventricular administration of clonidine (BOLME et a!., 1975).…”

Reduced renovascular resistance by clonidine

“…Most investigations have been done on animals and have reported the renal effects of short-term clonidine administration. In a short-term study in monkeys, Bolme et al 5 reported a decrease in blood flow to skin and skeletal muscle with maintenance of circulation to the hepatic and renal arteries during the first hour. Clonidine induced a decline in RBF in dogs with renal hypertension.…”