Nitric oxide synthesis inhibitors attenuate calcitonin gene-related peptide endothelium-dependent vasorelaxation in rat aorta.

The effect of inhibitors of nitric oxide synthesis were examined on the endothelium-dependent relaxation induced by acetylcholine and human alpha-calcitonin gene-related peptide (CGRP) on rat isolated aortic rings preconstricted with noradrenaline. The endothelium-dependent vasorelaxation induced by acetylcholine and CGRP was inhibited by NG-monomethyl-L-arginine (L-NMMA) and NG-nitro-L-arginine (L-NOARG) in a concentration-related fashion. The inhibition of endothelium-dependent relaxation by L-NMMA and L-NOARG was partially reversed by L-arginine but not by D-arginine for both acetylcholine and CGRP. The data presented suggests that CGRP, like acetylcholine; relaxes the rat aorta via the release of nitric oxide.