RGS9 overexpression in rods does not improve temporal contrast sensitivity. (A) Schematic details of the custom wheel-running visual behavioral apparatus, reprinted with permission from Naarendorp et al. (2010). (B) Photograph of the behavioral apparatus, with the mouse on the running wheel with the LED delivering the green flickering light mounted above. Flicker detection was measured by the trained mouse exiting the wheel and licking the water spout mounted above the elevated steel wire floor (left side of cage), completing a circuit and creating a TTL pulse recorded by the computer. Actual trials were performed in a completely dark room, and the cage was surrounded by an opaque-white ventilated enclosure illuminated from within by adjustable intensity white lights (bottom left of the picture), mounted below the floor level of the cage to avoid direct illumination. (C) Representative frequency of seeing curves for an RGS9-ox transgenic mouse and a WT littermate performing the nocturnal wheel-running assay for flicker detection. (D–F) Contrast sensitivity (inverse of the contrast producing 50% correct trials) for both strains was similar, though RGS9-ox mice showed more narrow frequency tuning, reflecting impaired visual performed at higher frequencies. The impairment at 10 Hz was significant (*, P < 0.05) regardless of whether data from the same absolute stimulus intensity were compared (D; 50 R*/rod/s) or whether the light intensities were adjusted to produce equivalent PDE activation (E and F), owing to the faster deactivation of the transducin–PDE complex in the RGS9-ox mice (Fortenbach et al., 2015). (E) 23 and 50 R*/rod/s for WT and RGS9-ox mice, respectively. (F) 50 and 104 R*/rod/s for WT and RGS9-ox mice, respectively. Error bars represent SEM.