Different timing and brain location of mPer1 and mPer2 proteins during earlier and later daily clock shifts

Light exposure alters Per gene expression in specific regions of the mouse suprachiasmatic nucleus (SCN) during subjective night.

• Phase delays occur with light pulses in early subjective night, while phase advances happen in late subjective night.
• mPer1 is expressed throughout the subjective night in the VIP-containing 'core' region of the SCN.
• mPer2 expression is induced only in early subjective night within the core region.
• In the 'shell' region of the SCN, phase delaying light pulses trigger significant mPer2 expression, while phase advancing pulses result in substantial mPer1 induction.
• Light pulses during mid-subjective night do not induce mPer1 or mPer2 in the shell region.
• Behavioral phase shifts are associated with the spread of light-induced Per gene expression from the core to the shell SCN.

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