Immobilization of intramembrane charge in Myxicola giant axons.

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Abstract
Immobilization of gating charge was examined in Myxicola giant axons dialyzed with Cs+. With increasing pulse durations the ratio QOFF/QON decreases to as little as 0.25 with a time constant of 3.2 ms as determined from composite data. Na inactivation time constants measured in the same axons ranged from 0.8-1.5 ms. A slow component of QOFF tends to appear as QOFF/QON decreases. Both QON and QOFF may be decreased by a prepulse with no change in their time course. In this case the time course of the decrease is similar to that observed for INa [intracellular Na]. The normalized steady-state charge immobilization curve is shifted in the depolarized direction by 15-20 mV from the normalized Na inactivation curve.