FIGURE 2.

Eye-drop administration of CNO activates DREADDs in vivo similar to IP. (A) Experimental approach. AAV carrying a Cre-dependent G_q-DREADD was injected into the right eye of mice with Cre expression in ipRGCs (Opn4^Cre mice). 3–5 weeks later, CNO was administered by eye-drop to the left eye or by IP injection. (B) DREADD activation is visualized by measuring pupil constriction in response to 1 μl CNO (1 mg/kg). (left) Baseline pupil size before CNO. (right) Pupil constriction observed in response to CNO applied directly to the left uninfected eye. (C) Dose-response curves for CNO applied via IP injection or eye-drop. Four doses were administered: 0.001, 0.01, 0.1, and 1.0 mg/kg. Data fit with a sigmoidal curve (n = 10, mean ± SD). Additionally, CNO eye-drops were administered to mice lacking DREADD virus injection (n = 6, mean ± SD). (D) CNO dose required for half-maximal constriction (EC₅₀) determined for both eye-drop and IP injection. EC₅₀ extracted from the sigmoidal curve fits for each mouse (points are individual mice, lines connect EC₅₀ values for the same mouse). Statistical significance determined by a non-parametric Wilcoxon matched-pairs signed ranked test (P = 0.0195).