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Temporal expression of seven clock genes in the suprachiasmatic nucleus and the pars tuberalis of the sheep: Evidence for an internal coincidence timer
Daily patterns of seven internal clock genes in the brain’s main and seasonal timing centers of sheep suggest an internal coincidence timer
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Abstract
The expression of seven clock genes was measured every 4 hours over 24 hours in the brain and pituitary of female Soay sheep under different light conditions.
- All clock genes were expressed in the suprachiasmatic nucleus (SCN) and the pars tuberalis (PT) of the pituitary gland.
- Clock and Bmal1 showed a 24-hour rhythm in the SCN, while Per1 and Per2 exhibited cycles out of phase with them.
- Photoperiod influenced the expression of Per1 and Per2, resulting in prolonged elevated levels during long daylight hours.
- In the PT, the expression of several clock genes, except CK1 epsilon, displayed high-amplitude 24-hour cycles affected by photoperiod.
- The timing of expression peaks varied, with Per1 and Per2 peaking during the day and Cry1 and Cry2 peaking early at night.
- Melatonin was linked to changes in the phase relationship of clock gene expression in the PT, suggesting different models of photoperiod influence.
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