Charge movement and membrane capacity in frog muscle.

Abstract

The transient current required to impose a step charge of potential in frog muscle has a complex time course especially in the region of internal potential between -50 and -40 mV. Examination of non-linear transient current in this voltage range suggests 2 components of charge movement: an initial more-or-less exponential movement and a slower component with a complex time course. Measurements of membrane capacity support such a division and confirm the steeper voltage dependence of the slower charge movement. Permanent depolarization to -40 mV appears to immobilize the slowly moving charge. Depolarization to -20 mV immobilizes both charge movements and uncovers the presence of a 3rd charge which seems to correspond to charge 2.