Neurogenic vasodilation in canine uterine and iliac arteries.

Abstract

To investigate neurogenic control of uterine and iliac arterial tone with reference to nerve-derived nitric oxide. Mechanisms underlying the response to perivascular nerve stimulation were studied under alpha-adrenoceptor blockade. Mechanical responses to nerve stimulation by nicotine were isometrically recorded in isolated canine uterine and iliac arterial strips. Nitric oxide synthase was stained immunohistochemically. The arterial strips responded to nicotine mainly with a contraction, which was reversed to a relaxation by prazosin. The responses were abolished by hexamethonium. The relaxation was not influenced by timolol and atropine but was suppressed by NG-nitro-L-arginine, a nitric oxide synthase inhibitor; the inhibition was reversed by L-arginine. Internal iliac arterial strips also responded to nicotine with a relaxation under prazosin treatment, the magnitude of which was appreciably less than that in the uterine artery. Histochemical study demonstrated that perivascular nerve fibres exhibit nitric oxide synthase immunoreactivity. Canine uterine arteries are innervated by adrenergic, vasoconstrictor and nitroxidergic vasodilator nerves, and the neurogenic vasodilation is evidently more marked than that in other canine arteries, including the iliac artery.