Switched single-electrode voltage-clamp amplifiers allow precise measurement of gap junction conductance |
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Authors: | Muller, Andreas Lauven, Melani Berkels, Reinhard Dhein, Stefan Polder, Hans-Reiner Klaus, Wolfgang |
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Abstract: | Measurement of gapjunction conductance(gj) with patch-clampamplifiers can, due to series resistance problems, be subject toconsiderable errors when large currents are measured. Formulas developed to correct for these errors unfortunately depend on exactestimates of series resistance, which are not always easy to obtain.Discontinuous single-electrode voltage-clamp amplifiers (DSEVCs) wereshown to overcome series resistance problems in single whole cellrecording. With the use of two synchronized DSEVCs, the simulatedgj in a modelcircuit can be measured with a maximum error of <5% in all recordingsituations investigated (series resistance, 5-47 M ; membraneresistance, 20-1,000 M ; gj, 1-100nS). At a very lowgj of 100 pS, theerror sometimes exceeded 5% (maximum of 15%), but the error wasalways <5% when membrane resistance was >100 M . The precisionof the measurements is independent of series resistance, membraneresistance, and gj. Consequently,it is possible to calculategj directly from Ohm's law, i.e., without using correction formulas. Our results suggest that DSEVCs should be used to measuregj if largecurrents must be recorded, i.e., if cells are well coupled or ifmembrane resistance is low. |
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