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Excerpt
Changes in light/dark cycle profoundly disrupt circadian rhythm. Therefore, we used a sub-chronic jet-lag (CJL) protocol over 2.5 weeks to test whether disturbing the biological clock leads to a depression-like phenotype in male NMRI-mice. The CJL protocol consisted of light/dark (LD) cycles in which the dark-phase alternated between 12 and 4 h every second day, while the light-phase was maintained at 12 h. Controls were kept at normal 12/12 h LD cycles. Home cage activity was continuously recorded using infrared sensors. Body weight and fur status were determined. Behavioral tests were performed after 2.5 weeks of CJL.
Activity profiles were markedly disturbed in CJL mice, indicating that the CJL protocol affects the circadian clock. In the elevated plus-maze, all parameters were unchanged. Animals only displayed a tendency towards increased latency to first open-arm entry. Neither fur status and body weight nor forced swimming was affected by CJL.
Our data demonstrate that exposure to CJL for 2.5 weeks leads to profoundly altered activity patterns without significantly affecting performance in the forced-swim test and elevated plus-maze. We are currently studying the effects of extended exposure to CJL in different models and mouse strains.
