Figure 2. Single channel activity of Kir4.1 currents.

A, single channel activity was recorded from another inside-out patch under the same conditions as in Fig. 1. Although no channel opening was detected at a membrane potential (V_m) level of 100 mV (not shown), this channel showed a high channel activity at V_m of −120 mV with P_open at 0.887 (top). In long-lasting openings, brief closures can be seen which are better illustrated on extended time scales (a, b). Traces a and b are obtained from positions a and b indicated by lines below the top trace, respectively. Calibration: 2 s for the top trace and 100 ms for traces a and b; 2 pA for all. Labels on the right side: c, closed state; o, open state. B, all points histogram of Kir4.1 currents shows channel openings at 2.5 pA at a membrane potential of −120 mV. Data are obtained from A as a stretch of recording of 20 s which was fitted by Gaussian distributions with peaks at 0.00 and 2.49 pA.