Fig. 3. Biophysical properties of KCNK5 currents in Xenopus  oocytes studied with two-electrode voltage clamp. (A  and B ) Whole-cell currents of KCNK5 cRNA-injected oocytes perfused with either frog Ringer’s solution (FR) or high-potassium frog Ringer’s solution (HK). Voltage pulses (1 s duration) are from −140 to +40 mV from a holding potential of −80 mV (inset ). (C ) Steady state current–voltage curves for FR (filled circles) and HK (open circles). (D ) Intracellular pH. Current–voltage curves in the presence or absence of 1 mm 2,4-dinitrophenol.