QUANTITATIVE-ANALYSIS OF DUAL WHOLE-CELL VOLTAGE-CLAMP DETERMINATION OF GAP JUNCTIONAL CONDUCTANCE

The dual whole-cell voltage-clamp technique is used widely for determi nation of kinetics and conductance of gap junctions. The use of this t echnique may, however, occasion to considerable errors. We have analys ed the errors in steady state junctional conductance measurements unde r different experimental conditions. The errors in measured junctional conductance induced by series resistance alone, and by series resista nce in combination with membrane resistance, were quantified both theo retically and experimentally, on equivalent resistive circuits with kn own resistance values in a dual voltage-clamp setup. We present and an alyse a method that accounts for series resistance and membrane resist ance in the determination of true junctional conductance. This method requires that series resistance is determined during the experiment, a nd involves some calculations to determine membrane resistance. We dem onstrate that correction for both membrane and series resistance reduc es the error in measured junctional conductance to near zero, even whe n membrane resistances on both sides of the gap junction are as low as 20 M Omega and the (true) junctional conductance is as high as 100 nS .