A comparison of calcitonin gene-related peptide effects on coronary flow and cardiac conduction system in the guinea pig.

The purpose of this study was to examine the effects of calcitonin gene-related peptide (CGRP) on coronary flow and various parts of cardiac conduction system (CCS) in the isolated guinea pig heart by recording the cardiac electrogram and His bundle activity simultaneously. The coronary flow (CF) was measured and the right atrium was paced at incremental frequencies periodically. Perfusing heart with CGRP at the concentrations of 3 30 nmol/L increased CF strikingly and dose-dependently. CGRP (30 nmol/L) caused a moderate and significant increase in the spontaneous heart rate, but failed to influence the atrioventricular nodal and His bundle-Purkinje fiber conduction time and the longest atrial pacing cycle length inducing 3 2 Wenckebach and 2 1 AV nodal conduction. The results indicate that CGRP in the guinea pig heart might act mainly on coronary vessels and then the sinus node, but did not affect the conductivity and refractoriness of the AV conduction system.