Voltage clamp with double sucrose gap technique. External series resistance compensation.

In this paper we deal with the double sucrose-gap voltage clamp technique. To perform a reliable clamp or to analyze the intracellular potential distribution, any external series resistance in the artificial node must be taken into account for it induces an instability in the external potential as soon as a current develops. A circuit was designed to compensate for this error, it has been found effective on an analog model and on experimental uni- or multicellular preparations. The attenuation in series resistance frequently causes ringing in the step response. This behavior was studied theoretically and also simulated with analog models where a selective bridged-T network was found to represent the electrical characteristics of the preparation when associated with the chamber and control electronics. A residual series resistance was found and is considered to be a part of the preparation. Characteristics necessary to obtain best results are proposed, for a preparation to be studied in experiments utilizing the double sucrose gap technique with external series resistance compensation.