Electrophysiologic effects of berberine on isolated sinoatrial and atrioventricular nodes of rabbit

Berberine (Ber) 0.1-30 mumol/L decreased the APA, Vmax, maximal depolarization potentials (MDP) and rate of spontaneous impulse initiation in sinoatrial node (SAN) and atrioventricular node (AVN) cells with prolongation of APD50, APD95 and ERP in a dose-dependent manner. The depression of SAN function was shown by increasing sinus cycle length (SCL), sinus recovery time (SRT) as well as corrected sinus recovery time (CSRT). In atria (crista terminalis, CT) higher concentrations of Ber were needed to prolong APD50, APD95, and ERP as compared with SAN and AVN. The effects of Ber on SAN were not antagonized or reversed by atropine (1 mumol/L), alpha 2-receptor agonist BHT-920 (10 mumol/L) or alpha 1-receptor agonist phenylephrine (10 mumol/L), but those effects of Ber on SCL, APA and Vmax could be reversed by norepinephrine (0.1 mumol/L). In calcium free Tyrode's solution, the inhibitory effects of Ber still revealed on SAN but on atria only prolongations of APD50 and APD95 were observed.