Modulation of Retinal Dopamine Signaling

Dopamine receptor agonist cocktail contained D1 receptor agonist (SKF38393; Abcam, Cambridge, UK) and D4 receptor agonist (PD168077; Tocris, Bristol, UK) dissolved in saline. Mice kept under SD conditions were i.p. injected with dopamine agonist cocktail (1 mg/kg) 1 h before the ERG recording under dim red light, as described previously^{18 (link)}. Dopamine receptor antagonist cocktail contained D1 receptor antagonist (SCH 23390; Tocris) and D4 receptor antagonist (L-745870; Abcam) (1 mg/kg each) dissolved in saline. Mice kept under LD conditions were i.p. injected with dopamine antagonist cocktail 1 h before ERG recording under dim red light. Based on previous reports^{46 (link),47 (link)}, modafinil (M6940; Sigma-Aldrich, St. Louis, MO, USA), dissolved in 0.1% DMSO/saline, was injected by gavage (64 mg/kg, 4 h apart, three times each day during daytime for 3 days). Forskolin (66575-29-9; Wako, Osaka) dissolved in saline (1%) was administered to the eyes (2 µl each) as eye-drops using a pipet (4 h apart, three times each day during daytime for 3 days). The effects of topical administration of Forskolin were examined twice by different experimenters, and consistent results were obtained in both experiments.