Figure 5.

Adenosine A2aR and dopamine D4R regulation of photoreceptor Cx36 phosphorylation in a mouse eyecup preparation. A, Dose–response curves for the A2aR agonist CGS21680 and the D4R antagonist L-745870 to phosphorylate Cx36 in light-adapted daytime retina. Data are means ± SEM; n = 3 per condition. B, In daytime under photopic light exposure, activating A2aR with 10 μm CGS21680 or blocking D4R with 3 μm L-745870 increased Cx36 phosphorylation. These effects were blocked by concurrently applying 10 μm PKA inhibitor Rp-8-CPT-cAMPS. Applying only 10 μm Rp showed no changes from the control group. Data are means ± SEM; n = 3–12 per condition. C, In daytime dark-adapted retina, inhibiting A2aR with 75 nm CSC or stimulating D4R with 200 nm PD168077 inhibited Cx36 phosphorylation. These inhibitory effects were reversed by 10 μm PKA activator Sp-8-cpt-cAMPS; 10 μm Sp alone showed no changes from the dark-adapted control retina, while 10 μm Rp significantly reduced phosphorylation of Cx36 in the OPL. Data are means ± SEM; n = 5–8 per condition. *p < 0.05; **p < 0.01; ns not significant.