Figure 12.

Following maintained darkness goldfish cones exhibit red, green or blue spectral sensitivity in the day, but at night spectral sensitivity is similar to that of rods. (A,B) Cone spectral sensitivity resembled that of rod during the night in the dark and in the day following spiperone application, but not in the day in the dark or in the light. These results demonstrate that rod-cone gap junctions are function all open at night in the dark and in the day following blockade of D₄Rs, functionally closed in the day. (A) Average spectral sensitivity of cones recorded under dark-adapted conditions during the day or subjective day fit one of three nomograms (thin dotted curves) corresponding to the three major known types of goldfish cone pigments: L, M, and S. Data were obtained from recorded red cones (open squares), green cones (open circles) and blue cone (open triangles). In contrast, the spectral sensitivity of all dark-adapted cones recorded at night peaked at ~535 nm (filled circles). The cone spectral sensitivity at night under dark-adapted conditions closely fit a modified nomogram that combines goldfish rod and L-cone pigment nomograms (dotted thick curve; λ_max = 537 ± 3 (SD) nm; r² = 0.91). Following application of spiperone (10 μM; open diamonds), cone spectral sensitivity in the subjective day resembled that observed during the subjective night and data points fit well the modified nomogram (λ_max = 537 ± 3 nm; r² = 0.96). (B) Following bright light adaptation at night or during the subjective nightthree groups of cones with different spectral sensitivities were observed: red cones (filled squares), green cones (filled circles) and blue cone (filled triangles), whereas bright light adaptation during the day or subjective day did not affect the relative spectral sensitivity of the cones (red cones: open squares; green cones: open circles) but slightly decreased the absolute sensitivity. Nomograms as in (A). Data points represent average sensitivity ± SEM. Modified from Ribelayga et al. (2008).