Melanopsin Regulates Both Sleep-Promoting and Arousal-Promoting Responses to Light
(A) Mice entrained to an LD12:12 cycle were exposed to 405 nm (violet), 470 nm (blue), and 530 nm (green) light at ZT14 in a light/dark box for 10 min. (B) In the first 1 min of the test, mice spent significantly more time in the hidden zone under blue light compared to violet, green, or control (dark) conditions. One-way repeated measures ANOVA for light condition, F(3.25) = 20.696, p ≤ 0.001. Post hoc Tukey dark versus violet p = 0.006, dark versus blue p = 0.021, dark versus green p ≤ 0.001, blue versus violet p ≤ 0.001, blue versus green p ≤ 0.001. (C) In the following 9 min, mice exposed to blue light continued to spend more time in the hidden zone compared to violet or green light. One-way repeated measures ANOVA light condition over time 2–-10 mins, F(3,25) = 11.721, p ≤ 0.001. Post hoc Tukey dark versus violet p = 0.635, dark versus blue p = 0.021, dark versus green p = 0.635, violet versus blue p ≤ 0.001, blue versus green p ≤ 0.001. (D) Opn4-/- mice (open bars) showed different responses to both blue and green light. In the first minute of the test, in comparison with wildtype mice, Opn4-/- mice spent less time in the hidden zone in response to blue light. However, Opn4-/- animals spent more time in the hidden zone compared with wildtype under green light. Two-way repeated measures ANOVA for light condition and genotype, light condition x genotype interaction F(1,26) = 20.585, p ≤ 0.001. Post hoc Tukey wildtype versus Opn4-/- blue p = 0.010, green p = 0.001. (E) Whilst the attenuated response to blue light in Opn4-/- mice persisted over the remaining time course of the test (one-way repeated measures ANOVA for effect of genotype over time, F(1.13) = 14.376, p = 0.002), no difference was observed between wildtype and Opn4-/- mice under green light (one-way repeated measures ANOVA for effect of genotype over time, F(1.13) = 0.26, p = 0.617). Opn4-/- mice showed no statistical difference in responses to wavelength in the first minute or whole time of the test (one-way repeated measures ANOVA for effect time over wavelength F(9,81) = 0.976 p = 0.466). Histograms reflect mean percentage ± SEM of time spent in the dark box of the light dark box during the 10 min trial (n = 6–-10/group wildtype, n = 4–-10 Opn4-/-). Significant differences indicated by *** p ≤ 0.001, ** p ≤ 0.01, * p ≤ 0.05, NS = not significant. The data used to make this figure can be found in S3 Data.