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

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. 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 (EC 50 ) was 2.11 ± 1.35 × 10 −9 m . 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 ). 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.