Abstract: Objactive To investigate the effects of benzyltetrahydropalmatine and methoximine on delayed rectifier potassium current (Ik) in guinea pig ventricular myocytes. Methods Whole-cell patch clamp technique was used to record Ik current. Results Methoximine 50 μmol·L^-1 augmented densities of Ik and Ik,tail from (12.4±1.8)pA pF^-1 and (4.2±0.5 )pA pF^-1 to (20.5±0.7)pA pF^-1 and (7.2±0.6)pA pF^-1 respectively. The effect of methoximine on the Ik and Ik,tail can be reversed by BTHP 30 μmol·L^-1, with the inhibition rates of 62.9%±4.3% and 61.1%±3.7%, respectively. When the cells were exposed only to 30 μmol·L^-1 BTHP, Ik and Ik,tail were blocked by 37.5%±6.0% and 35.9%±5.5%. Conclusion The results show that BTHP can inhibit the enhancing effect of methoximine on Ik in guinea pig ventricular myocytes.

Key words: Benzyltetrahydropalmatine, Benzyltetrahydropalmatine, Methoximine, Methoximine, Delayed rectifier potassium current, Delayed rectifier potassium current, Patch-clamp technique, Patch-clamp technique, Myocytes, Myocytes