VASODILATOR EFFECTS OF CLONIDINE ON THE MESENTERIC ARTERIAL BEDS IN NORMOTENSIVE AND SPONTANEOUSLY HYPERTENSIVE RATS

Clonidine, an alpha(2)-agonist, caused a concentration-dependent vasod ilation of the mesenteric arterial beds in both normotensive and hyper tensive rats. The clonidine-induced vasodilation was inhibited by N-G- nitro-L-arginine, and the inhibition was reversed by L-arginine. The c oncentration-dependent vasodilation was not significantly different be tween normotensive and hypertensive rats. These results suggest that c lonidine has an endothelium-dependent vasorelaxant action in the resis tance artery such as rat mesenteric arterial bed, and the endothelium- dependent vasodilator effects of clonidine in the mesentery may be inv olved in the depressor effect of the drug.