Ramp protocol for recording Kir2.1 currents. (A) Voltage protocol and current trace (experiment R1). The voltage protocol (red line) consists of a 100-ms prepulse at −200 mV, a 400-ms positive ramp (Pos) from −200 to +200 mV, a 100-ms interramp plateau phase at +200 mV, and a 400-ms negative ramp (Neg) from +200 to −200 mV. The ionic current (colored blue for Pos segment; orange for Neg segment; otherwise black) was recorded from an inside-out patch with symmetrical 20 mM [K⁺]. (B) Scaled G-V curves obtained from I-V relationships determined from the double ramp protocol using the formula G(V) = scale ⋅ I(V)/(V − V_os) − G_min (Table 1). Ramp segments are color-coded the same as in A. (C) Conductance Hill plot (W_H[g]) constructed from the G-V curves in A. Red arrows demarcate the outer linear asymptotic regions used for fitting.