Quantitative analysis of dual whole-cell voltage-clamp determination of gap junctional conductance.

The dual whole-cell voltage-clamp technique is used widely for determination of kinetics and conductance of gap junctions. The use of this technique may, however, occasion to considerable errors. We have analysed the errors in steady state junctional conductance measurements under different experimental conditions. The errors in measured junctional conductance induced by series resistance alone, and by series resistance in combination with membrane resistance, were quantified both theoretically and experimentally, on equivalent resistive circuits with known resistance values in a dual voltage-clamp setup. We present and analyse a method that accounts for series resistance and membrane resistance in the determination of true junctional conductance. This method requires that series resistance is determined during the experiment, and involves some calculations to determine membrane resistance. We demonstrate that correction for both membrane and series resistance reduces the error in measured junctional conductance to near zero, even when membrane resistances on both sides of the gap junction are as low as 20 MOmega and the (true) junctional conductance is as high as 100 nS.