Figure 2.

Silent TWIK-1 K⁺ channels conduct Rb⁺ or NH₄⁺ currents. (A and B) Whole-cell currents of TWIK-1 channels were sequentially recorded from the same transfected CHO cell in bath solutions containing 5 mM K⁺ and 135 mM Na⁺ (black line), 140 mM K⁺ (orange line), 5 mM K⁺ and 135 mM Rb⁺ (pink line), and 140 mM Rb⁺ (blue line). (C) Summary of currents measured at −140 mV in panels A and B in bath solutions containing 140 mM K⁺ (orange bar) or 140 mM Rb⁺ (blue bar) (−311 ± 53 pA vs. −10,843 ± 1850 pA, n = 4). (D and E) Experiments similar to those in panels A and B were performed except that NH₄⁺ replaced Rb⁺. (F) Summary of currents measured at −140 mV in panels D and E in bath solutions containing 140 mM K⁺ (orange bar) or 140 mM NH₄⁺ (purple bar) (−323 ± 88 pA vs. −13,761 ± 4046 pA, n = 4). (^∗P < 0.001).