ROMK current under high-K conditions. Mice were fed a diet with 3% K for 6–8 d. Currents were measured before and after the addition of 0.1 µM TPNQ to the superfusate. Difference currents (I_SK) represent currents through ROMK. (A) Currents in a cell from region 2. (B) Currents in a cell from region 4.