Whole-cell patch-clamp recordings
Na+ currents were recorded using low-resistance,
fire-polished electrodes (≈ 1MΩ) made from 8161 Corning borosilicate
glass coated with HIPEC (Dow-Corning, Midland, MI, USA) to minimize
electrode capacitance. An Axopatch 200 amplifier and pClamp software
(Molecular Devices, Sunnyvale, CA, USA) were used to record
Na+ currents. The series resistance was compensated to
80% to minimize voltage-clamp errors. The cells were allowed to
stabilize for 5 min after the whole-cell configuration was established.
The membrane potential was held at –140mV before the currents were
recorded. Sodium Currents were filtered at 5 kHz and digitized at 83.33
kHz. The liquid junction potential was not corrected. All the
experiments were performed at room temperature (22°C).