Fig. 6: The sleep-promoting effect of 40 Hz light flickering is mediated by ENT2, but not ENT1, in mice.

a Representative hypnograms and EEG spectra of WT littermates after treatments with normal light and 40 Hz light flickering, respectively. b The time course of SWS during the entire dark phase after light flickering was recorded and analyzed in WT littermates. c The amount of SWS in the first 2 h was compared between WT littermate mice subjected to 40 Hz flickering and normal light, and statistical significance (*P < 0.05) was evaluated using Student’s t-test (n = 4). d Representative hypnograms and EEG spectra of ENT2-KO mice after treatments with normal light and 40 Hz light flickering, respectively. e The time course of SWS during the entire dark phase after light flickering was recorded and analyzed in ENT2-KO mice. f The amount of SWS in the first 2 h was compared between ENT2-KO mice subjected to 40 Hz flickering and normal light, and statistical significance (*P < 0.05) was evaluated using Student’s t-test (n = 9). g Representative hypnograms and EEG spectra of ENT1-KO mice after treatments with normal light and 40 Hz light flickering, respectively. h The time course of SWS during the entire dark phase after light flickering was recorded and analyzed in ENT1-KO mice. i The amount of SWS in the first 2 h was compared between ENT1-KO mice subjected to 40 Hz flickering and normal light, and statistical significance (*P < 0.05; **P < 0.01) was evaluated using Student’s t-test (n = 9). The time course of SWS was analyzed using two-way ANOVA, while the difference in the total sleep amount each hour was analyzed with a paired Student’s t-test. *P < 0.05 was considered significant. Data are presented as mean ± SEM.