Basilar arterial construction caused by intracisternal NG-nitro-L-arginine in anesthetized monkeys.

The present study was designed to determine whether tonic nitric oxide (NO)-mediated vasodilator innervation participates in basilar arterial dilatation in the anesthetized Japanese monkey.The basilar arterial diameter was angiographically measured, and NG-nitro-L-arginine (L-NNA), a nitric oxide synthase inhibitor, was intracisternally applied.The injection of L-NNA produced a sustained constriction of the basilar artery, the effect being reversed by the cisternal injection of L-arginine. The vasoconstriction tended to be accelerated by treatment with phentolamine. Under alpha-adrenoceptor blockade, hexamethonium significantly attenuated the vasoconstrictor response to L-NNA. Intracisternal injections of this inhibitor did not alter the systemic blood pressure and heart rate.These findings suggest that construction by the NO synthase inhibitor of the monkey basilar artery is associated with suppression of synthesis of NO in vasodilator nerves receiving tonic impulses from the central nervous system. The basilar arterial tone appears to be regulated by nitroxidergic and adrenergic nerves and by NO derived from the endothelium in anesthetized monkeys.