Effects of berberine on conductivity of heart

In isolated guinea pig sinus node and crista terminalis cells, berberine, (Ber) 10 mumol.L-1 shortened the S-C and C-H intervals; increased the membrane responsiveness accompanying in the dose dependent inhibition of action potentials of these cells. The sinus cells were more sensitive to the depressive effect of Ber than crista terminalis cells. Similarly, after iv Ber (10 mg.kg-1), the intervals of A-H and H-V were decreased; whereas AERP and AVNFRP prolonged on His bundle electrogram in anesthetized rabbits. The above results indicate that Ber possessed a positive dromotropic effects on both intra-atrial and atrioventricular conductions, which were independent to increase of Vmax and APA. Thus the actions of Ber might be relevant to its effects on myocardial cell membrane by decreasing impedence and increasing electric coupling. Furthermore, Ber 15 mg.kg-1 iv in rabbits caused a severe myocardial inhibition.