Temporal and spatial distribution of immunoreactive PER1 and PER2 proteins in the suprachiasmatic nucleus and peri-suprachiasmatic region of the diurnal grass rat (Arvicanthis niloticus)

Both PER1 and PER2 proteins were detected in the suprachiasmatic nucleus (SCN) of the unstriped Nile grass rat, peaking early in the dark phase.

• The SCN serves as the primary circadian pacemaker in both diurnal and nocturnal mammals.
• PER1 and PER2 expression patterns suggest that mechanisms regulating behavior differ between day-active and night-active animals.
• Rhythmic expression of PER1 and PER2 was also observed in the lower subparaventricular zone (LSPV) of the grass rat.
• The findings support the idea that the LSPV may contribute to circadian regulation in diurnal species.
• Additional rhythmic expression was noted in areas lateral to both the LSPV and the SCN.

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