Fig. 3

Estrus cycle and opto-SD-induced grimace. Mouse grimace score (MGS) was determined at 75 lx (room lighting) and with increasing light intensity between 400–8400 lx, (A). Data shown in (B) and (C) are grimace scores plotted against increasing light intensity using the square root of lux values. Fit with a simple linear regression, there is no difference in slopes between sham and opto-SD grimace-light intensity curves (F = 0.30, p = 0.585). Opto-SD produced a significant elevation in the grimace-light intensity curve (F = 117, ^#p < 0.0001 vs sham, B). Using three-way ANOVA, there was a significant effect of opto-SD (F = 90.82, p < 0.0001), light intensity (F = 3.82, p = 0.001) and estrus cycle stage (F = 5.19, p = 0.024) on grimace score (C). Grimace-light intensity curves demonstrated significantly non-zero slopes^‡ for animals in PE sham (F = 11.17, p = 0.001), MD opto-SD (F = 5.56, p = 0.022), and PE opto-SD (F = 8.04, p = 0.005)] groups. However, MD sham animals did not have a significant slope of the grimace-light intensity curve, suggesting this group did not experience as much photosensitivity (F = 1.27, p = 0.266). There was no significant difference in the elevation (F = 0.23, p = 0.635) or slope (F = 0.35, p = 0.553) within the opto-SD groups between MD versus PE cycle stages