BmTx3B, a novel scorpion toxin from Buthus martensi Karsch, inhibits delayed rectifier potassium current in rat hippocampal neurons.

AIM To examine the effect of BmTx3B, a novel short-chain peptide isolated from the venom of Asian scorpion Buthus martensi Karsch, on voltage-gated potassium channels. METHODS Two types of voltage-dependent potassium currents were recorded from dissociated hippocampal neurons of neonatal rat in whole-cell voltage-clamp mode, and separated based upon their kinetic properties. RESULTS BmTx3B (10-100 micromol/L) selectively inhibited the delayed rectifier potassium current (I(K)), without affecting the fast transient potassium current (I(A)). The inhibition of the peptide on I(K) was reversible, concentration-dependent and voltage-independent. BmTx3B did not affect the steady-state activation and inactivation kinetics of the current. CONCLUSION The short-chain scorpion peptide BmTx3B selectively blocked the delayed rectifier potassium channel.