Constant light reduces daily cycles of a key clock gene and protein in the brain’s internal clock area of mice

mPER2 protein lost its rhythmicity in the suprachiasmatic nucleus after 7 days of constant light conditions.

• Constant light and constant dark conditions cause a free-running period and reduce activity in rodent circadian rhythms.
• The circadian expression rhythm of mPer2 mRNA in the suprachiasmatic nucleus was dampened under constant light conditions.
• In constant light, the expression peak of mPER2 protein was moderately delayed.
• Under constant dark conditions, the circadian expression of mPer2 and mPER2 protein was slightly attenuated and advanced.
• LL or DD housing did not alter mPer2 gene expression or its product in the cerebral cortex.
• The findings indicate that mPER2 circadian expression in the suprachiasmatic nucleus is associated with behavioral circadian rhythms under both light conditions.

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