科研之友
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摘要
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.
- 出版日期2016-10
