Rod recovery from bright flashes is rate limited by RGS9 expression in vivo. (A) Photoresponse recovery from saturating flashes of increasing strength from an RGS9-ox mouse (top, squares) and a WT mouse (bottom, circles). Colors denote the flash strengths corresponding to the points in B. Note that the timescale of the bottom panel is twofold longer than that of the top panel. (B) Times for the photoresponses in A to recover to 60% of their dark-adapted value (dashed lines in A) as a function of the natural logarithm of the number of photoexcited rhodopsin molecules (R*/rod) elicited by the test flash. When there is translation invariance in the recovery of responses (Nikonov et al., 1998), the slope of the fitted line gives the dominant time constant of recovery (τ_D). (inset) Individual τ_D determinations (red points) and means (given by the height of the bars) for the two different genetic backgrounds (n = 3 mice each). Black points in the inset correspond to the values obtained from the data in A and B.