Effects Of Polypeptides Purified From Chinese Buthus Martensi Karsch On Sodium, Potassium Channels In Rat Dorsal Root Ganglion Neurons

Part one: Effects of BmK2-2-5-6 on Na+, K+ channels in rat dorsal root ganglion neuronsWhole-cell patch clamp technique was used in this study to investigate the effects of BmK2-2-5-6 on Na+ and K+ currents in rat DRG neurons. The results indicated that BmK2-2-5-6 exerted its effect on the inactivating phase of Na+ channel but no effect on peak Na+ current at a concentration of 100ug/ml. It slowed inactivating of Na+ channel. At the same concentration, BmK2-2-5-6 inhibited outward potassium currents(Ik) in rat DRG neurons. The outward potassium currents were inhibited45.3+7% ( n=3 ) with BmK2-2-5-6 application. These effects were reversible with washout.Part two: Effects of BmK2-2-5-6-l on potassium currents in rat dorsal root ganglion neuronsWe have used the patch-clamp method in the whole-cell configuration to investigate the effect of BmK2-2-5-6-1 on the outward potassium current (Ik) and rectified delayed potassium current (IKDR) in rat dorsal root ganglion (DRG) neurons. Different from other k+ toxins, BmK2-2-5-6-l displayed dual-action on potassium currents. At low concentrations (10-50u.g/ml) induced a dose-dependent increasing of these currents. Outward potassium currents (IK) were increased to 158.4+9%, 131.8+5%, 118.5+2% with 10, 30, 50ug/ml BmK2-2-5-6-l respectively. These effects were dose- and time-dependent, and the I-V curve demonstrated that these effects were voltage-independent. However, at high concentrations (50-100ug/ml), it inhibited outward potassium currents (IK). IK was inhibited by 58.7+6 % ( n = 3 ) at a concentration of 100ug/ml with BmK2-2-5-6-1 application. Due to the limited amount of toxin obtained, the dose-response relationship of BmK2-2-5-6-1 at high concentrations on IK was not determined.It averagely spent 3-5 min from administration to reach to maximal effect, which indicated that BmK2-2-5-6-l would be bind to the polezone of potassium channels or the inner of membrane.These results indicated that BmK2-2-5-6-l would be proposed to represent a novel subfamily of k+channel toxins.