RESPONSES TO PERIVASCULAR NERVE-STIMULATION OF DISTAL TEMPORAL ARTERIES FROM DOGS AND MONKEYS

In helical strips of dog distal superficial temporal artery denuded of endothelium and partially contracted with prostaglandin F2alpha (PGF2 alpha), nicotine produced a moderate relaxation preceded by no contrac tion or a slight contraction. The contraction was less than that obser ved in proximal arterial strips obtained from the same dogs and was ab olished by alpha-adrenoceptor antagonists. Relaxations under alpha-rec eptor blockade were greater in the distal than in the proximal arterie s. Treatment with N(G)-nitro-L-arginine (L-NA), a nitric oxide (NO) sy nthase inhibitor, abolished the relaxation caused by nicotine and tran smural electrical stimulation (5 Hz for 40 s), the response being reve rsed by L- but not by D-arginine. In monkey temporal arteries of the d istal and proximal portions treated with alpha-antagonists, nicotine p roduced similar magnitudes of relaxation, which were abolished by trea tment with the NO synthase inhibitor. Vasodilator nerves appear to pla y an important role in regulation of small arterial tone; noradrenergi c vasoconstrictor function is less and vasodilator nerve function is m ore evident in dog distal arteries than in dog proximal arteries. The neurally induced relaxation in dog and monkey distal temporal arteries is postulated to be mediated by NO derived from nerves.