Melanopsin Regulates Both Sleep-Promoting and Arousal-Promoting Responses to Light
(A–C) Sleep induction in response to violet (A), blue (B) and green (C) light. Sleep was studied in Opn4-/- mice (open symbols, n = 6–10/group) and compared with wildtype mice (WT, solid symbols). (D) In comparison with wildtype mice, Opn4-/- mice show delayed sleep onset in response to green and violet light but advanced sleep onset in response to blue light. Two-way ANOVA for wavelength and genotype, wavelength x genotype interaction F(2,43) = 12.143, p ≤ 0.001. Posthoc Tukey wildtype versus Opn4-/- violet p = 0.011, blue p = 0.013, green p ≤ 0.001. Comparison of Opn4-/- responses in sleep induction as well as duration show no statistical differences due to wavelength. (E) However, in comparison to wildtype mice Opn4-/- mice exposed to green and violet light show reduced sleep duration. Two-way ANOVA for wavelength and genotype, wavelength x genotype interaction F(2.44) = 5.142, p = 0.010, posthoc Tukey wildtype versus Opn4-/- violet p = 0.017, blue p = 0.259, green p = 0.003. Despite the difference in sleep onset under blue light in Opn4-/- and wildtype mice, there was no difference in sleep duration. Solid horizontal bars illustrate light pulse duration from ZT14 until ZT15. Data plotted as mean ± SEM. 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 S2 Data.