Dark rearing slows rod response recovery at eye opening. Rod-dominated ERGs from normal-reared and dark-reared retinas at P14. (A and B) Dark rearing does not alter the rod-dominated b-wave amplitude or sensitivity. Initial stimuli provided short (1–8 ms) flashes of 520 nm light (delivering 0.19–13,280 photons µm⁻²). (B) Population averaged b-wave amplitudes from normal-reared (nr, closed circles; n = 12 retinas) and dark-reared (dr, open circles; n = 12 retinas) mice plotted against flash intensities. (C) Dark-rearing reduces the b-wave:a-wave ratio at dim light intensities. Ratios were averaged from normal-reared (nr, closed circles; n = 12 retinas) and dark-reared animals (dr, open circles; n = 12 retinas) and plotted as a function of light intensity. (D) Dark-rearing slows the recovery phase of the rod-dominated a-wave but does not alter the phototransduction amplification rates. Blockers were perfused, and the 10 strongest flashes from A elicited a-waves (red traces). Insets: Activation phase of the a-waves taken from the region indicated by the black bracket on an expanded time scale (t = 0–100 ms). These a-waves were normalized to R_max after the nose component and fit (superimposed gray traces) with the activation model of phototransduction (Eq. 4) to obtain amplification constants (A; s⁻²). The dashed horizontal indicates response saturation (R_max) after the nose component. (E) Dark-rearing slows the recovery phase of the rod-dominated a-wave but does not alter sensitivity. Population averaged a-wave amplitudes, along with their recovery times from saturation, in normal-reared (closed symbols; n = 12 retinas) and dark-reared (open symbols; n = 12 retinas) retinas plotted against flash intensities. Intensity–response relationships were best-fit with Eq. 2 and appear as follows: nr (solid green), dr (dashed green). Vertical lines = half-saturating intensities (I_1/2). Average time constants (τ_D) were then obtained from a Pepperberg analysis and compared linear fit values (black line) giving the following values: (P14: n = 12, P = 0.0049, τ_nr = 121 ± 38 ms, τ_dr = 239 ± 90 ms). (F) Dark rearing does not alter the synaptic transfer function. Representative synaptic transfer functions from a single normal-reared and dark-reared retina were fit with Eq. 6 and appear as follows: nr (solid green), dr (dashed green). Vertical lines = half-saturating a-wave values (solid line: k_nr = 18.8 µV; dashed line: k_dr = 17.4 µV). Error bars represent mean ± SEM. Single and double asterisks indicate P values of <0.05 and <0.01, respectively.