Differential effects of nitric oxide synthase inhibitors on endothelium-dependent and nitrergic nerve-mediated vasodilatation in the bovine ciliary artery

Overend, J. and Martin, W. (2007) Differential effects of nitric oxide synthase inhibitors on endothelium-dependent and nitrergic nerve-mediated vasodilatation in the bovine ciliary artery. British Journal of Pharmacology, 150(4), pp. 488-493.

Abstract

<i>Background</i> <i>and</i> <i>purpose</i>: We have previously demonstrated that L-NMMA (N^G-monomethyl-L-arginine) selectively inhibits vasodilatation produced by endothelium-derived nitric oxide but not nitrergic nerves in the bovine penile artery. The present study investigated whether L-NMMA had a similar selective action in the bovine ciliary artery. We also investigated whether two recently introduced inhibitors of neuronal nitric oxide synthase (nNOS), AAAN (N-(4S)-4-amino-5-[aminoethyl]aminopentyl-N′-nitroguanidine) and L-NPA (N^G-propyl-L-arginine), produced selective blockade of vasodilatation induced by nitrergic nerves but not endothelium-derived nitric oxide. <i>Experimental</i> <i>approach</i>: Rings of bovine ciliary artery were suspended in a wire myograph for tension recording. Neurogenic (nitrergic) vasodilatation was elicited by electrical field stimulation, and endothelium-dependent, nitric oxide-mediated dilatation was evoked using bradykinin. <i>Key</i> <i>results</i>: L-NMMA inhibited vasodilatation induced by endothelium-derived nitric oxide but not the nitrergic nerves. In fact, L-NMMA, acted like L-arginine in protecting nitrergic vasodilatation against inhibition by L-NAME (N^G-nitro-L-arginine methyl ester). AAAN had no effect on vasodilatation induced by either nitrergic nerves or endothelium-derived nitric oxide, but L-NPA inhibited both with equal potency. <i>Conclusions</i> <i>and</i> <i>implications</i>: In the bovine ciliary artery, L-NMMA acts as a selective inhibitor of the vasodilatation induced via endothelial NOS, without affecting that operating via nNOS. Furthermore, the putative nNOS inhibitors, AAAN and L-NPA failed to produce the expected selective inhibition of nitrergic vasodilatation in this artery.

• Item Type: Articles
• Keywords: artery, autonomic nerves, EDHF, endothelium, endothelium-derived hyperpolarizing factor, nitrergic nerves, nitric oxide, nitric oxide synthase, vasodilatation
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Martin, Professor William
• Authors: Overend, J., and Martin, W.
• Subjects: Q Science > QP Physiology
• College/School: College of Medical Veterinary and Life Sciences > School of Life Sciences
• Journal Name: British Journal of Pharmacology
• ISSN: 1476-5381