Thin wall borosilicate glass

The cells expressing K_V1.3 and K_V7.4 were digested and plated on glass coverslips before current recording. The HEKA EPC10 amplifier (HEKA Elektronik, Ludwigshafen, Germany) was used to record currents in whole cells under the control of PATCHMASTER software (HEKA Elektronik, Ludwigshafen, Germany). A thin-wall borosilicate glass (A-M Systems) was used to pull patch pipettes and then the pipettes were fire-polished to 3–4 megohm. For whole-cell recordings, the capacity current was minimized by amplifier circuitry, and the series resistance was compensated by 30% to 65%. For K_V1.3 and K_V7.4 channel, intracellular solution contained 140 mM KCl, 10 mM EGTA, 2 mM MgCl₂, 1 mM CaCl₂, 10 mM HEPES (pH 7.3, adjusted with KOH), and extracellular solution contained 150 mM NaCl, 0.5 mM CaCl₂, 5 mM KCl, 1.2 mM MgCl₂, 10 mM HEPES (pH 7.3, adjusted with NaOH), and the current traces were tested by a 1000-ms depolarizing pulse of 10 mV from a holding voltage of −80 mV. The Hill logistic equation shown below was used to fit the Dose–response curves:
where n is an empirical Hill coefficient, and fmax is the fraction of current resistant to inhibition at high toxin (Tx) concentration.