THE POTASSIUM CURRENT UNDERLYING DELAYED RECTIFICATION IN CAT VENTRICULAR MUSCLE

1. Outward currents in cat ventricular fibres have been studied using the single sucrose gap method. The time dependent outward currents can be separated into a fast component, IK, and a slow component, Ix. The voltage dependence of the IK time constant was bell‐shaped, being about 150 msec at ‐90 mV, 500 msec at ‐25 mV and 300 msec at +30 mV. The combination of much faster time constants and larger amplitudes relative to Ix allowed the estimation of IK amplitude, but not time course, from semilog plots of membrane currents accompanying 2 sec depolarizations.

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