Procedure 2: Calculation of the membrane resistance (Rm)
Cells were held at -60 mV in voltage-clamp mode. Ten steps to -65 mV (1s duration @ 1 Hz) were generated and recorded on fifteen separate electrophysiological traces and a median trace was calculated. The Rm was calculated on the median trace according to ohm’s low R=ΔV/ΔI where ΔV=-5mV and ΔI was the difference between the median current in the last 100 ms of the hyperpolarization and the median current in the 200 ms pre-step period. Access resistance AR was calculated as AR=ΔV/ΔIA where ΔIA is the difference between the peak of transient current and the median current in the 200 ms pre-step period.