[Electrophysiological effects of calcitonin gene-related peptide on isolated sinoatrial node of the rabbit].

The purpose of this study was to investigate the electrophysiological effects of calcitonin gene-related peptide (CGRP) on the pacemaker cell of rabbit sinoatrial node (SAN) and to determine whether I(Ca) is involved in the effects. Action potentials (AP) were recorded from the isolated SAN with microelectrode technique. It was found: (1) CGRP (1 nmol/L) had no effect on AP configuration; CGRP (10 nmol/L) increased the maximal diastolic potential, AP amplitude and depolarization velocity of 0 and 4 phases, and decreased sinus cycle length and AP duration. After applying CGRP for 20 min the above effects reached to a maximum. (2) CGRP (100 nmol/L) caused arrhythmia in the SAN. (3) Calcium channel antagonists, CdCl2 and verapamil attenuated the electrophysiological changes in AP of SAN induced by CGRP (20 nmol/L). The results indicate that a calcium-dependent mechanism may underlie the CGRP effects.