Forskolin increases the dominant time constant of the PDE shut-off. Plot of the time of recovery from saturation (T_rec) as a function of the flash intensity in the log scale in normal (○) and forskolin-containing (•) solution. T_rec is defined as the time of regaining 20% of dark current. Straight lines are an approximation of experimental points with T_rec = c + τ_D*ln(I). Numbers at the lines show corresponding dominant recovery time constants, τ_D. The cell with the biggest effect of forskolin is shown. Records in forskolin solution were started after 15 min of perfusion.