Whole eyeballs of mice were isolated and fixed in 4% (wt/vol) paraformaldehyde in PBS for 20 minutes. Retinas were dissected and refixed with 4% (wt/vol) paraformaldehyde for an extra 15 minutes. Retinas were then dehydrated in 30% (wt/vol) sucrose and embedded in embedding medium (Neg-50, Thermo). 12-µm-thick cryosection slides were obtained and stored at −80 °C. For immunostaining, cryosection slides were placed at room temperature, washed with PBS, blocked in blocking buffer (4% BSA, 0.5% Triton X-100 in PBS) for 45 minutes, treated with primary antibody at 4 °C overnight, and then incubated with secondary antibody at room temperature for 1 hour. Then primary and secondary antibodies were used as follows: rabbit anti-Cone arrestin (1:50, Millipore, AB15282), mouse anti-Rhodopsin (1:500, Sigma, O4886), rabbit anti-Recoverin (1: 500, Millipore, AB5585), rabbit anti-Pkcα (1:100, Sigma, P4334), rabbit anti–glutamine synthetase (1:200, Abcam, ab73593), mouse anti–glial fibrillary acidic protein (1:200, Santacruz, sc-33673), mouse anti–cellular retinaldehyde binding protein (1:200, Abcam, ab15051), mouse anti-GFP (1:200, Invitrogen, 3E6), goat anti-Flag (1:200, Abcam, ab1275), and guinea pig anti-vGlut1 (1:100, Millipore, AB5905). Donkey anti-rabbit IgG conjugated to Alexa Fluor 488 (1:200, Life Technologies), donkey anti-mouse IgG conjugated to Alexa Fluor 594 (1:200, Li-cor Biosciences), Donkey anti-rabbit IgG conjugated to Alexa Fluor 680 (1:200, Life Technologies), and goat anti-guinea pig IgG conjugated to Alexa Fluor 568 (1:200, Abcam) were used as secondary antibodies. Samples were stained with 4,6-diamidino-2-phenylindole and visualized using laser-scanning confocal microscope (TCS SP8, Leica). Images were taken at 200 to 400 µm location in reference to the optic nerve.