For sodium currents (INa), whole-cell patch-clamp recordings were obtained as described previously.7 (link),8 (link) INa was elicited in 100-ms steps to –30 mV from holding potentials of –100 to –70 mV. Currents were measured before and after propafenone (300 nM or 1 μM; Sigma-Aldrich, Gillingham, UK), dronedarone (5 and 10 μM; Sigma-Aldrich, Gillingham, UK), and flecainide (1 μM; Sigma-Aldrich, Gillingham, UK). These concentrations are consistent with those previously reported in the literature.7 (link),9 (link),10 (link) Cells were paced at 1 Hz while the drugs were introduced to the perfusate.
Action potentials (APs) were recorded at 36°–37°C in the whole-cell current-clamp configuration and triggered by 2-ms current injections (1.5 nA). AP trains were stimulated at 1 Hz. APs were recorded at RMPs from –90 to –65 mV by varying the background current injection. Action potential amplitude (APA) and peak AP phase 0 upstroke velocity (dV·dt-1) were analyzed using modified algorithms from ElectroMap.11 (link)
Action potentials (APs) were recorded at 36°–37°C in the whole-cell current-clamp configuration and triggered by 2-ms current injections (1.5 nA). AP trains were stimulated at 1 Hz. APs were recorded at RMPs from –90 to –65 mV by varying the background current injection. Action potential amplitude (APA) and peak AP phase 0 upstroke velocity (dV·dt-1) were analyzed using modified algorithms from ElectroMap.11 (link)
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