Altered Rhythm of Adrenal Clock Genes, StAR and Serum Corticosterone in VIP Receptor 2-Deficient Mice

The adrenal clock gene rhythm in VPAC2 receptor-deficient mice is phase-advanced by approximately 6 hours compared to wild type mice during a light/dark cycle.

• Mice lacking the VPAC2 receptor exhibit disrupted circadian rhythms in physiology and behavior.
• Per1 and Bmal1 mRNA showed a 24-hour rhythmic expression in the adrenal gland of wild type mice under both light/dark and dark conditions.
• In constant darkness, the adrenal clock gene rhythm in VPAC2 receptor-deficient mice became arrhythmic.
• A significant 24-hour rhythmic variation in adrenal Star mRNA expression and serum corticosterone concentration was observed during the light/dark cycle.
• The loss of rhythmicity in adrenal clock gene expression and serum corticosterone levels in VPAC2-KO mice occurred after transfer to constant darkness.
• Double immunohistochemistry confirmed that the PER1 protein and StAR were co-localized in the same steroid-producing cells.

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