Dynamics of potassium ion currents in squid axon membrane. A re-examination.

The original experiments of Cole and Moore (1960. Biophys. J. 1:161-202.), using conditioning and test membrane potentials to examine the dynamics of the potassium channel conductance in the squid axon, have been extended to test voltage levels by the use of tetrodotoxin to block the sodium conductance. The potassium currents for test voltage levels from -20 to +85 mV were superposable by translation along the time axis for all conditions tested: (a) with depolarizing conditioning voltages; (b) with hyperpolarizing conditioning voltages; and (c) in normal and in high potassium external media. The only deviations from superposition seen were when the internal sodium concentration was abnormally high and the potassium currents showed saturation at high levels of depolarization. Some restoration toward normal kinetics could be obtained by rapidly repeated depolarizations.