Potassium ion currents in the crayfish giant axon. Dynamic characteristics.
The kinetics of the voltage-sensitive potassium channel in crayfish axon have been examined. The conductance increase after a step depolarization from rest can be described by a first-order kinetic process raised to the third power. When conditioning voltage levels preceded the test pulse, the steady-state conductance was found to be independent of initial conditions. Depolarizing conditioning voltages in general allowed superposition of test voltage potassium currents by a shift along the time axis. Hyperpolarizing conditioning voltages produced a delay in onset of conductance during the test pulse and changed the kinetics so that superposition was not possible. The delay increased during the hyperpolarization with a first-order lag having a time constant in the range of 1.5-3 ms. Return to the resting level caused recovery from the delayed state to follow a single exponential decay with a time constant of 1.9-2.2 ms. The steady state delay vs. voltage curves were not saturated at potentials as negative as -180 mV.
D000818:Animals; D003400:Astacoidea; D001369:Axons / Q000502:physiology*; D004594:Electrophysiology; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D011188:Potassium / Q000378:metabolism*
D007473:Ion Channels; D011188:Potassium