Opiate component in the realization of the vascular effects of clonidine

Systemic and regional hemodynamic changes (microsphere technique) were studied in urethan-chloralose anesthetized cats after intravenous clonidine and naloxone administration in different sequence. It was shown that antihypertensive effect of clonidine was caused by a decrease in the cardiac output and an increase in the total peripheral vascular conduction. The ability of clonidine to increase total peripheral conduction was completely blocked with naloxone preadministration. It was concluded that endogenous opiate receptors take part in the vasodilating clonidine effect in abdominal organs.