Figure 1. Schematic diagram showing the timing of retina explant cultures. Solid white and black boxes at the top left show the lighting schedule to which animals were exposed before sacrifice (white: 12 h light, black: 12 h dark). All cultures were started at zeitgeber time 12 (ZT12), corresponding to the beginning of the night period and were maintained in constant dark. Alternating black and hatched rectangles thereafter indicate the projections of the previous lighting schedule (black: dark, hatched; light). In the M0 protocol, retina explants were cultured on Neurobasal A medium (with luciferin when adequate) throughout the experiment, without any medium change. The time window corresponding to retina sampling for qPCR analysis is shown with a double arrow. In the M1 protocol, retinas were incubated on Neurobasal A for 24 h and then transferred to 199 medium supplemented with luciferin. In the M2 protocol, retinas were incubated on Neurobasal A during 24 h as in M1, transferred to 199 medium for 24 h, and the medium was again refreshed after 24 h and supplemented with luciferin. The time windows during which the bioluminescence data were analyzed are shown with the dashed double arrows.