Conduction through Kir1.1 channels in inside-out patches with symmetrical Rb⁺ concentrations. (A) Inward currents with −100 mV across the patch at different [Rb⁺]. (B) i-V relationships for different [Rb⁺]. Lines through the data points have no theoretical meaning. (C) Single-channel currents at −100 mV as a function of ion concentration. The line represents the best fit of Eq. 1 to the data, with i_max = 1.8 ± 0.1 pA and K_m = 26 ± 4 mM. (D) i_max and K_m, measured as in C, as a function of voltage.