Histological and Functional Studies on the Nitroxidergic Nerve Innervating Monkey Cerebral, Mesenteric and Temporal Arteries

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Abstract
Nitroxidergic nerves and their functional role were determined in a variety of monkey arteries. Nitric oxide synthase-immunoreactive nerve fibers innervating the monkey arterial wall were histochemically determined by the use of nitric oxide synthase antiserum. Thin nitric oxide synthase-immunoreactive fibers were consistently found in the outer media of monkey cerebral, mesenteric and temporal arteries, in addition to many thicker fibers and nerve bundles in the adventitia. In the monkey pterygopalatine ganglion, the immunoreactivity was clearly seen in nerve cells, bundles and fibers. Helical strips of monkey arteries were exposed to the bathing media for tension recordings and were stimulated by electrical square pulses. In helical strips of the cerebral artery denuded of the endothelium, transmural electrical stimulation produced relaxations that were abolished by tetrodotoxin or NG-nitro-L-arginine, a nitric oxide synthase inhibitor. In the monkey mesenteric and temporal arterial strips treated with α-adrenoceptor antagonists, the relaxation caused by electrical stimulation was also abolished by the nitric oxide synthase inhibitor, and it was restored by L-arginine. Nitroxidergic perivascular nerves, histologically demonstrated, appear to play an important role in dilating the monkey cerebral artery and in counteracting a vasoconstriction associated with noradrenergic nerve activation in the mesenteric and temporal arteries.