Figure 3.

Phosducin knock-out reduces response compression but not stimulus scaling during b-wave light adaptation. A, The values for flashes evoking half-saturating rod-driven b-wave amplitudes, I_0.5, taken from Tables 1 and 3 were normalized to the dark-adapted values, I_{0.5, dark}, and plotted as functions of background luminance. The data for WT mice are shown in black, for Pd^−/− mice in red and Gγ₁^+/− mice in violet. The background luminance values for Pd^−/− and Gγ₁^+/− mice were further corrected to account for the reduced dark-adapted b-wave light sensitivity in these animals, as described in Results. The straight dashed line represents the best fit to all three datasets. B, Normalized maximal amplitudes of rod-driven b-wave stimulus–response curves in Tables 1 and 3 (R_max/R_{max rod, dark}) are plotted as functions of background luminance. The values for background strength for Pd^−/− and Gγ₁^+/− mice were corrected as in A. Solid lines represent data fits to Equation 2 (WT and Gγ₁^+/− combined, I_half = 0.043 ± 0.003 cd/m², n = 0.40 ± 0.02; Pd^−/−, I_half = 0.085 ± 0.008 cd/m², n = 0.54 ± 0.03; error bars represent SEM). C, The R_max/I_0.5 ratios for rod-driven b-waves were normalized to their dark-adapted values and plotted as functions of background luminance. The values for background strength in Pd^−/− and Gγ₁^+/− mice were corrected as in A. Solid lines represent data fits to Equation 2 (WT and Gγ₁^+/− combined, I_half = 0.001 ± 0.001 cd/m², n = 0.60 ± 0.04; Pd^−/−, I_half = 0.004 ± 0.001 cd/m², n = 0.63 ± 0.03).