Abstract： Objective　To investigate what effects BmKAS-1 (a polypeptide purified from the Chinese scorpion Buthus martensi Karsch ［BmK］ and named as BmK activator of skeletal-muscle ryanodine receptor) and its upstream mixture BmK1-3-2 have on Na+ channels in dorsal root ganglion (DRG) small diameter neurons.Methods　The whole-cell patch-clamp technique was used to investigate the effects of BmKAS-1 and BmK1-3-2 on Na+ current in rat small diameter DRG neurons.Results　About 50% peak Na+ current was suppressed by 10*!μg/ml of BmK1-3-2. 1.62*!μg/ml of BmKAS-1 also blocked 50% peak Na+ current, and there was an obvious dose-dependent relationship.Conclusion　Both BmK1-3-2 and BmKAS-1 have a blocking effect on Na+ channels, and this may one of the mechanisms for the analgetic effect of BmK1-3-2 and BmKAS-1.