Figure 1.

The retinas of mice lacking NRL have a functional cone visual cycle. A, Cone trans-retinal ERG responses from dark-adapted Nrl^−/− retina (left) and bleached retinas followed by different recovery times in darkness. The red traces represent the light responses elicited by 276,511 photons · μm⁻² at 500 nm. B, Kinetics of cone sensitivity recovery. Retinas were exposed to brief bleaching light at time 0. It took 4 h for Nrl^−/− cones to recover their sensitivity to the plateau at ∼50% of its dark-adapted value (black trace, open squares), while WT cones recovered their sensitivity after an identical bleach to the same level within 10 min (blue trace, filled squares). Data were fitted by a single exponential function with τ = 84 min for Nrl^−/− cones and τ = 4.5 min for WT cones. To determine the effects of 11-cis-retinol on the recovery of cone sensitivity, retinas were treated with 100 μm 11-cis-retinol in 0.1% ethanol and incubated at room temperature for 30 min. Exogenous 11-cis-retinol promoted rapid cone dark adaptation (red, open triangle). Sensitivity measurements were normalized to the corresponding dark-adapted value. Error bars indicate SEM; n = 3. C, Post-bleach recovery of Nrl^−/− cone sensitivity was accelerated by exogenous 11-cis-retinol. Cone sensitivity reached the maximum level within 30 min. The red traces represent the photo responses elicited by 276,511 photons · μm⁻² at 500 nm.