[Action of batrachotoxin on the membrane sodium channels of neuroblastoma cells].

Currents through normal and batrachotoxin (BTX)-modified sodium channels of dialyzed neuroblastoma cells were measured under voltage clamp conditions. BTX is shown to induce a shift of voltage range of activation toward more negative potentials by 25-40 mV and the appearance of steady-state sodium conductance. BTX-modified sodium channels retain the ability to partial inactivation. It is evidenced by partial decay of the current during maintained depolarization and by dependence of current size and kinetics on prepulses. BTX induces changes in channel selectivity. Permeability ratios determined from reversal potential measurements are: Na : NH4 : K = 1 : 0.70 : 0.29 and 1 : 0.35 : 0.11 for BTX-modified and normal channels, respectively.