Clock gene activity in the brain’s main and other timing centers during rhythm splitting in CS mice

The CS mouse exhibits spontaneous splitting in the circadian locomotor rhythm under continuous darkness.

• Circadian rhythmicities of clock genes mPer1, mBMAL1, and mClock in the suprachiasmatic nucleus do not change during rhythm splitting.
• The expression of the mPer1 gene is bimodal in the piriform and cingulate cortices and peaks in line with the two split components of the behavioral rhythm.
• Findings suggest that the site of rhythm splitting may be outside the suprachiasmatic nucleus.
• Alternatively, different subregions or other clock genes within the suprachiasmatic nucleus could be involved in the rhythm splitting.

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