Repeated Psychosocial Stress at Night Affects the Circadian Activity Rhythm of Male Mice

Repeated social defeat during the dark phase significantly alters activity rhythms in mice.

• Mice exposed to repeated social defeat during the dark phase displayed increased activity and body temperature during the stress exposure.
• Post-stress, SDD mice had a reduced initial activity bout and delayed activity onset compared to control mice.
• In contrast, repeated social defeat during the light phase did not impact the activity rhythms.
• Differences in activity patterns between SDD and SDL mice suggest long-lasting effects on the biological clock.
• These effects appear to involve the clock genes Per1 and Per2, as they were absent in clock-deficient mutant mice.

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