Disclosure of inwardly rectifying K+conductance in dual patch recording. (a, b) Bath application of 100 μM Ba2+ produce a moderate VM inhibition but not noticeable inhibition of inward currents using the conventional single electrode recording, although the VM depolarizes by 2.6 mV with full recovery. Whole cell currents were induced by voltage steps from -210 to 30 mV with 30 mV increments. A pre-pulse voltage at 0 mV/300 ms was used to maximally activate Kir4.1 currents (inset). (c) Application of 100 μM BaCl2 in dual patch induces a significant increase in RM. (d) An example shows I-VM relationships before (black) and after (red) 100 μM Ba2+ application. Ba2+ sensitive currents were resolved by subtraction of currents in the presence of Ba2+ application from the control. (e) A negative VM-dependent GM increase is inhibited totally by 100 μM Ba2+. Voltage dependent Ba2+ sensitive conductances are shown in (f).