Steady state current noise from the intrinsic gating of inward rectifier channels

Steady-state current noise from the intrinsic gating of inward rectifier channels in the eggs of the marine polychaete Neanthes arenaceodentata was recorded under voltage clamp conditions. Lorentzian-shaped power spectra with corner frequencies near 1 Hz and zero-frequency asymptotes of 1 - 5 X 10(-23) A2/Hz were obtained for test potentials 15-45 mV positive to EK in solutions containing 10-40 mM Ko. The spectra are compatible with the predictions of a three-state kinetic model for inward rectification in which the single channel rectification is independent of voltage. The single channel conductance derived from this interpretation is 8 pS with 40 mM Ko.