Fig. 2

Protocol for original recording of intramembrane charge movements. a Pulse protocol used to extract current carried by intramembrane charge movements. The same pulse (P) was applied either from the holding potential (test, left) or superimposed on a hyperpolarizing prepulse (∆ Vpre; control, right). The pulse over the control voltage range is assumed to cause no intramembrane charge movement. b The total current recordings for the pulses in a. Traces in a and b were recorded as photos of oscilloscope display. c Difference between membrane current in the test pulse minus the current in the control pulse, obtained by digital subtraction of digital recordings of test and control currents using an analog to digital converter and a digital recording system. d Schematic diagram of the three microelectrode voltage clamp systems used in this experiment. All records obtained at the tendon termination of a muscle fiber in a frog sartorius muscle stretched to reduce contraction and bathed in solution to block or remove essentially all membrane conductance. From ref. [37], with modification