Figure 4.

Exposure to LL dampens PER oscillations in Drosophila clock neurons. Bioluminescence recordings of XLG-PER-Luc in cultured adult Drosophila brains (n = 6 brains) under 3 d of control LD, followed by 5 d of LL (red shade), then DD (gray shade). A, Averaged bioluminescence traces of all PER-expressing circadian neurons under 3 d of control LD, followed by 5 d of LL conditions (black trace, red shade) followed by DD (black trace, gray shade). B, Averaged bioluminescence traces of PER expression in circadian neuron subgroups under control LD-LL-DD conditions. Each neuron subgroup is labeled as follows: s-LNv (red), l-LNv (yellow), LNd (orange), DN1 (blue), and DN3 (green). C, Calculated synchronization index/order parameter, R values for PER oscillations (dotted trace) under LD-LL-DD conditions. XLG-PER-Luc (solid trace), under control conditions is overlaid for comparison (s-LNv = 18 cells, l-LNv = 19 cells, LNd = 18 cells, DN1 = 27 cells, DN3 = 18 cells). D, Statistical comparisons of overall synchrony of PER expression under control LD followed by DD and LD-LL-DD conditions. Difference in order parameter, R, between oscillations of PER in control LD or LD-LL-DD were calculated using a randomization analysis (black trace). Dark gray and light gray zones indicate 95% and 99% confidence bands, respectively, under the null hypothesis that there is no difference in order parameter, R, between the oscillations of PER under control LD conditions followed by DD and LD-LL-DD; values that fall outside the dark band are statistically significant.