Electrophysiological Measurements From Xenopus Oocytes

Standard recording solutions contained (mM) 110 NaCl, 2 CaCl₂, and 10 HEPES for pH ≥ 6.8. For solutions with a pH < 6.8, HEPES was replaced by 10 mM MES. The pH was adjusted using NaOH. For some experiments, Cl^– was completely replaced by the same concentration of SCN^–. Whole-cell currents from Xenopus oocytes were recorded by two-electrode voltage clamp (TEV-200A; Dagan Corporation) at -40 mV using Chartmaster software (HEKA Electronics) at a sampling rate of 1 ms and low-pass filtering at 2 kHz. Oocytes were placed in a RC-26Z recording chamber (Warner Instruments) and impaled with two glass electrodes filled with 1 M KCl, with a resistance of <0.5 MΩ. Oocytes were perfused at a rate of 5–15 ml/min. All experiments were performed at room temperature (20–25°C).