Reciprocal regulation by putatively nitroxidergic and adrenergic nerves of monkey and dog temporal arterial tone.

In monkey and dog superficial temporal artery strips denuded of the endothelium, transmural electrical stimulation and nicotine produced a contraction that was abolished by phentolamine and potentiated by NG-nitro-L-arginine (L-NNA), a nitric oxide (NO) synthesis inhibitor. The potentiation was reversed by L-arginine but not by its D-enantiomer. The arteries treated with phentolamine and contracted with prostaglandin F2 alpha responded to the electrical stimulation and nicotine with relaxations that were abolished by tetrodotoxin and hexamethonium, respectively, and were markedly inhibited by L-NNA but not by D-NNA, atropine, and timolol. The L-NNA-induced inhibition was reversed by L-arginine. Nicotine increased the level of guanosine 3',5'-cyclic monophosphate in the monkey arteries; the increment was prevented by L-NNA. It is concluded that the monkey and dog temporal arterial tone appears to be reciprocally regulated by adrenergic vasoconstrictor and nonadrenergic noncholinergic vasodilator nerves. The neurogenic relaxation would be mediated by NO that is possibly released from the vasodilator nerve and transmits information to smooth muscle; therefore the nerve may be called "nitroxidergic."