In order to calculate the actual trans-membrane voltage drop from the applied command voltage at supra-physiological voltages it was important to take into account the voltage drop at the access resistance, i.e. the junction between pipette and cell interior, (the so-called ‘voltage divider effect’; [8]). The applied command voltage (Vcomm) had to be corrected for this value to assess the actual trans-membrane voltage drop (VM) when a voltage pulse (∆Vcomm) was applied (for more details, see