Amiloride-sensitive currents in UNC-8(G387E)–expressing oocytes. (A) Example of ionic currents recorded in an oocyte expressing UNC-8(G387E) perfused with a NaCl physiological solution. Currents were elicited by voltage steps from −160 to +100 mV in 20-mV increments. The holding potential was −30 mV. (B) The same oocyte shown in A was perfused with NaCl physiological solution plus 1 mM amiloride. (C) Amiloride-sensitive currents. Currents obtained by subtracting the amiloride-resistant current from the total current are shown here. Dashed lines represent the zero current level. The outward amiloride-resistant current is likely oocytes endogenous current, which varies in amplitude from batch to batch of oocytes. (D) Current–voltage relationship of amiloride-sensitive currents in UNC-8(G387E)–expressing oocytes (n = 5). Note the strong inward rectification at negative voltages. The solid line represents the amiloride-sensitive current recorded from an oocyte injected with wild-type UNC-8. (E) Amiloride dose–response curve. Currents recorded in amiloride at −100 mV were normalized against the currents recorded in NaCl physiological solution at −100 mV. Data points were fitted by Hill equation, which gave a Ki of 7.8 µM and an n value of 0.5 (n = 6). Data are expressed as mean ± SE.