Determination and compensation of series resistances during whole-cell patch-clamp recordings using an active bridge circuit and the phase-sensitive technique
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We present a technique which combines two methods in order to measure the series resistance (R S) during whole-cell patch-clamp recordings from excitable and non-excitable cells. R S is determined in the amplifier’s current-clamp mode by means of an active bridge circuit. The correct neutralization of the electrode capacitance and the adjustment of the bridge circuit is achieved by the so-called phase-sensitive method: Short sine wave currents with frequencies between 3 and 7 kHz are injected into the cells. Complete capacitance neutralization is indicated by the disappearance of the phase lag between current and voltage, and correct bridge balance is indicated by a minimized voltage response to the sine wave current. The R S value determined in the current-clamp mode then provides the basis for R S compensation in the voltage-clamp recording mode. The accuracy of the procedure has been confirmed on single-compartment cell models where the error amounted to 2–3 %. Similar errors were observed during dual patch clamp recordings from single neocortical layer 5 pyramidal cells where one electrode was connected to the bridge amplifier and the other one to a time-sharing, single-electrode current- and voltage-clamp amplifier with negligible R S. The technique presented here allows R S compensation for up to 80–90 %, even in cells with low input resistances (e.g., astrocytes). In addition, the present study underlines the importance of correct R S compensation by showing that significant series resistances directly affect the determination of membrane conductances as well as the kinetic properties of spontaneous synaptic currents with small amplitudes.
KeywordsSeries resistance Bridge amplifier Whole-cell patch-clamp Neurons Astrocytes
We thank F. Rucker for mathematical support, G. Horn for technical assistance, R. Kurtz for valuable comments on the manuscript, and M. Sutor-Gauß for editing the manuscript.
BS would like to dedicate this manuscript to the 80th birthday of Prof. Dr. Gerrit ten Bruggencate.
Compliance with ethical standards
Conflicts of interest
HRP is an employee of npi electronic GmbH. TR and BS declare no conflicts of interest.
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