Two-electrode voltage-clamp solutions and recordings

For expression of monomeric KCNQ2 and KCNQ3 constructs in Xenopus laevis oocytes, complementary RNA was transcribed from the cDNA using the mMessage mMachine kit (Ambion). KCNQ2 and KCNQ3 in pTLN were linearized with MluI (KCNQ2) or HpaI (KCNQ3) and transcribed using the SP6 primer. Stage V–VI X. laevis oocytes were prepared as previously described (Shih et al., 1998) and injected with complementary RNA. Voltage-clamped potassium currents were recorded in a modified Ringer’s solution (in mM): 116 NaCl, 2 KCl, 1 MgCl₂, 0.5 CaCl₂, and 5 HEPES, pH 7.4, using an OC-725C voltage clamp (Warner). Glass microelectrodes were backfilled with 3 M KCl and had resistances of 0.1–1 MΩ. Data were filtered at 5 kHz and digitized at 10 kHz using a Digidata 1440A controlled by pClamp 10 software.