EFFECTS OF BERBERINE ON L-TYPE AND T-TYPE CALCIUM CHANNELS IN GUINEA-PIG VENTRICULAR MYOCYTES

AIM: To study the effects of berberine (Ber) on L-(I-Ca,I-L) and T-typ e (I-Ca,I-T) channels in isolated guinea pig ventricular myocytes. MET HODS: Using whole cell patch-clamp recording technique. RESULTS: Ber 1 0, 30 mu mol . L-1 inhibited the I-Ca,I-L from 1400 +/- 247 pA to 978 +/- 204 pA (n = 5 cells of 5 guinea pigs, P < 0.05), and to 664 +/- 17 9 pA (n = 5, P < 0.01), respectively. The inhibitory effect was concen tration-dependent and non-frequency-dependent. The peak value of I-Ca, I-L in the current-voltage relationship was decreased. Ber affected th e inactivation kinetics of I-Ca,I-L. The half activation potential (V- 0.5) was shifted from -27.8 mV to -34.2 mV and the slope factor (kappa ) was changed from 9.22 into 13.03. Ber did not affect the activation kinetics. Ber 10 and 30 mu mol . L-1 also inhibited I-Ca,I-T (from 154 +/- 80 pA to 101 +/- 78 pA, and to 48 +/- 45 pA, n = 8 cells of 5 gui nea pigs, P < 0.05). CONCLUSION: Ber possessed blocking effects on bot h Lr and T-type calcium channels.