Neurogenic vasodilation in canine uterine and iliac arteries

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Objective:To investigate neurogenic control of uterine and iliac arterial tone with reference to nerve-derived nitric oxide.Design:Mechanisms underlying the response to perivascular nerve stimulation were studied under α-adrenoceptor blockade.Methods:Mechanical responses to nerve stimulation by nicotine were isometrically recorded in isolated canine uterine and iliac arterial strips. Nitric oxide synthase was stained immunohistochemically.Results: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.Conclusion: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.

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