Effect of berberine on slow inward ionic current in guinea pig ventricular papillary muscle

Using a single sucrose gap voltage clamp technique, it was found that berberine hydrochloride (Ber-HCl) had a dose-dependent biphasic effect on Isi of guinea pig papillary muscle. It was more difficult to wash out the inhibitory effect of Ber-HCl on Isi. In the initial stage of the experiment, Ber-HCl 72 mumol/L and 365 mumol/L greatly improved the influx of extracellular Ca2+ and increased the amplitude of Isi. As the drug perfusion was prolonged, however, Ber-HCl dramatically blocked Ca2+ channels and decreased the influx of extracellular Ca2+ consequently, Isi was reduced in amplitude and later disappeared. This experiment further revealed the mechanisms of action of Ber on cardiac contractility and for the treatment of arrhythmias.