Clock Gene Expression in Adult Primate Suprachiasmatic Nuclei and Adrenal: Is the Adrenal a Peripheral Clock Responsive to Melatonin?

The adrenal gland shows a 9- to 12-hour antiphase pattern in clock gene expression compared to the suprachiasmatic nucleus.

• Bmal-1 expression peaks in the SCN during the dark hours (2000-0200 h) and during the day (1400 h) in the adrenal gland.
• Per-2 expression is higher in the SCN during the day (1400 h) and peaks in the adrenal gland at nighttime (around 0200 h).
• The oscillation of clock genes in the adrenal gland is associated with the rhythmic expression of the steroid-producing enzyme 3beta-hydroxysteroid dehydrogenase.
• Adrenal explants maintained oscillatory expression of Per-2 and Bmal-1 for at least 36 hours in culture.
• The timing of Per-2 and Bmal-1 expression was affected by 100 nm melatonin, which blunted their acrophase.

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