Calcitonin gene‐related peptide (CGRP) is a potent non‐endothelium‐dependent inhibitor of coronary vasomotor tone

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Abstract
1 Ring segments of bovine left circumflex coronary artery were pre-contracted with 5-hydroxytryptamine or phenylephrine and then exposed to increasing concentrations of calcitonin gene-related peptide (CGRP) and other drugs. 2 CGRP administration resulted in dose-dependent inhibition of induced tone. Maximal relaxation to CGRP was 89 ± 5% and the concentration required to achieve 50% maximal relaxation (EC50) was 2.11 ± 1.35 × 10−9 m. 3 CGRP-induced relaxation was not affected by removal of endothelial cells nor was it significantly altered by incubation of coronary vessels with atropine, propranolol, phentolamine (all 10−6 m) or indomethacin (10−5 m). 4 From these data we conclude that CGRP is a potent inhibitor of coronary artery vasomotor tone which appears to act directly on vascular smooth muscle rather than through the release of a secondary mediator. These data support the possibility that CGRP may play a role in non-adrenergic, non-cholinergic regulation of coronary artery tone.