Sodium channel inactivation in the crayfish giant axon. Must channels open before inactivating

摘要: Experiments on sodium channel inactivation kinetics were performed voltage-clamped crayfish giant axons. The primary goal was to investigate whether channels must open before inactivating. Voltage-clamp artifacts minimized by the use of low-sodium solutions and full series resistance compensation, spatial uniformity currents checked with a closely spaced pair electrodes used measure local current densities. For membrane potentials between -40 +40 mV, decay zero single exponential time-course. time constant for is steep function potential. time-course measured double-pulse method very similar at same Steady-state curves different test pulses are identical. double pulse shows lag that roughly correlates opening channels, but detailed comparisons course prepulse suggest it not strictly necessary Measurements potential dependence integral conductance area also inconsistent simplest cases models in which