Inward Rectifier K+ -Channel Kinetics from Analysis of the Complex Conductance of Aplysia Neuronal Membrane

摘要

Conduction in inward rectifier, Potassium ion-channels in Aplysia neuron and Bariumion blockade of these channels were studied by rapid measurement of the membrane complex admittance in the frequency range 0.05 to 200 Hz during voltage clamps to membrane potentials in the range -90 to -40 mV. Complex ionic conductances of K + and chlorine ion rectifiers were extracted from complex admittances of other membrane conduction processes and capacitance by vector subtraction of the membrane complex admittance during suppressed inward K+ current from complex admittances determined at other K+10 and membrane potentials. The contribution of the K + rectifier to the admittance is distinguishable in the frequency domain above 1 Hz from the contribution of the C1 - rectifier, which is only apparent at frequencies <0.1 Hz. The voltage dependence (-90 to -40 mV) of the chord conductance and the relaxation time of K + rectifier channels at K +10 = 40 mM were determined by curve fits of admittance data by a membrane admittance model based on the linearized Hodgkin-Huxley equations. The conductance of inward rectifier, K + channels at a membrane potential of -80 mV had a square-root dependence on external K + concentration, and the relaxation time increased from 2 to 7.5 ms for K + 10 = 20 and 100 mM, respectively. The relaxation time of the blockade process decreased with increase in Ba ++ concentration. Keywords: Squid, Axons. Reprints. (aw)