Recovery of sensitivity after a 50% bleach of the visual pigment. (A) Response families are shown for a dark-adapted cell and at steady state after a 50% bleach. Flash strengths were 2.6, 8.5, 26, 85, and 260 photons/µm² for the dark-adapted family, and 8.5, 26, 85, 260, and 850 photons/µm² for the post-bleach family. (B) The amplitude of the response was plotted versus the strength for the dark-adapted and bleached cell shown in A. (C) Changes in log sensitivity after pigment bleaching plotted as a function of time. A 50% bleach was given at time 0 s. Sensitivity before pigment bleaching is denoted by an upward filled triangle. Sensitivity was undetectably low during the period of time where the dark current remained totally suppressed. After this period, there was gradual recovery of sensitivity at both the base (filled circles) and tip (open circles) of the rod outer segment (plotted as mean ± SEM). These recoveries were fit with single-exponential functions that indicate the base recovers to steady state with a time constant of ∼250 s, and the tip with a time constant of ∼1,100 s. Sensitivity once steady state was reached is denoted by an upward open triangle. (D) Suction electrode–only recording configuration for the experiment. Superimposed lower traces show responses to saturating flashes at selected time points during recovery in C.