Observations on intramembrane charge movements in skeletal muscle

Using signal-averaging techniques, one can record small membrane currents which remain even after blockage of the ionic currents which accompany electrical excitation in muscle. These residual currents probably represent the reorientation of charged molecules inside the membrane in response to a change in membrane potential. Two operationally separable types of intramembrane charge movement in muscle are described, one of which may play a role in excitation—contraction coupling. Studies of tetrodotoxin binding to muscle indicate that ‘sodium gating current’ is unlikely to contribute significantly to either type of charge movement.