Figure 6. Action potential clamp recordings of I_Cl(Ca) in an SA node cell.

A, complete cycle of pacemaker activity of an SA node cell (C_m, 81 pF) recorded under current clamp conditions. B, currents recorded during reapplied pacemaker activity under voltage clamp conditions (‘action potential clamp’) in absence of DIDS (upper panel), in presence of 0.2 mm DIDS (middle panel), and upon wash out of the drug (lower panel). Inset shows current obtained by digitally subtracting the current trace recorded under wash out conditions from the one recorded under control conditions. C, DIDS-sensitive current I_Cl(Ca) obtained by digital subtraction of compensation currents in presence and after wash out of 0.2 mm DIDS. D, reconstructed current (I_m) flow during the cycle of pacemaker activity. Current was calculated by I_m = -C_m × dV/dt, where C_m is the membrane capacity of the cell. Note the different current scale.