Effects of berberine on potassium currents in acutely isolated CA1 pyramidal neurons of rat hippocampus

The effects of berberine, an isoquinoline alkaloid with antiarrhythmic action, on voltage-dependent potassium currents were studied in acutely isolated CA1 pyramidal neurons of rat hippocampus by using the whole-cell patch-clamp techniques. Berberine blocked transient outward potassium current (I-A) and delayed rectifier potassium current (I-K) in a concentration-dependent manner with EC50 of 22.94+/-4.96 muM and 10.86+/-1.06 muM, E-max of 67.47+/-4.00% and 67.14+/-1.79%, n of 0.77+/-0.08 and 0.96+/-0.07, respectively. Berberine 30 muM shifted the steady-state activation curve and inactivation curve of IA to more negative potentials, but mainly affected the inactivation kinetics. Berberine 30 muM positively shifted the steady-state activation curve of I-K. These results suggested that blockades on K+ currents by berberine are preferential for I-K, and contribute to its protective action against ischemic brain damage. (C) 2003 Elsevier B.V. All rights reserved.