An automatic voltage adjuster for a single microelectrode recording of the membrane potential and resistance

An automatic voltage adjuster was designed in order to apply an intracellular rectangular pulse of current and record the membrane potential simultaneously using a single intracellular microelectrode. The original voltage record consists of a rectangular signal signal (Va) due to the resistance of the microelectrode and a slowly rising signal (Vb) which is the proper value of the membrane potential shift produced by the application of the intracellular rectangular pulse of current. The instrument described in this paper samples the original signal (Va + Vb) at 0.5 approximately 1.0 ms after the application of the rectangular pulse of current, holds this voltage level (Va) and subtracts it from the original signal (Va + Vb) to obtain (Vb).