Experimental lighting schedules

Chronic jet-lag protocol

Adult (2-month old) C57bl/6 J WT male mice (Mus musculus) were housed individually with food and water ad libitum.

The chronic jet-lag (CJL) schedule was previously designed by our group (Casiraghi 2012) and consisted in a 6h advance of the LD cycle every 2 days (CJL6/2); which was accomplished through a 6h shortening of every second dark phase (Fig. 1).

Effective circadian desynchronization was evaluated by observation of a particular activity pattern which included two components of activity rhythms with periods of about 21h and 24.7h. General activity was detected by infrared sensors connected to a computer interface that records activity counts every five minutes for posterior time-series analysis (Archron, Buenos Aires, Argentina).

Zeitgeber time (ZT) was used as a temporal reference: ZT0 is the moment of lights on, and ZT12 the moment of lights off. For the CJL schedule, samples were taken during the 12-h night and on the following day

Figure 1. Schematic light schedules of LD12:12 and CJL6/2cycles. White bars represent the light time and the black bars represent the night time. Mice were subject to these light schedules for 3 weeks before tumor cells inoculation.

References

L. P. Casiraghi, G. A. Oda, J. J. Chiesa, W. O. Friesen, D. A. Golombek, Forced desynchronization of activity rhythms in a model of chronic jet lag in mice. Journal of biological rhythms 27, 59-69 (2012).