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Nature 417, 391-392 (23 May 2002) | doi:10.1038/417391a

Open Innovation Challenges

Circadian rhythms: A gut feeling for time

Michael H. Hastings

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Many body functions keep a daily rhythm, maintained by a central clock in the brain. But how does the clock communicate with the rest of the body? The small protein prokineticin 2 looks well placed to be the messenger.

Have you ever wondered how you can wake up automatically before the alarm clock rings? It is because your body's neural and physiological preparations for wakefulness are not just a response to the world outside, but are strictly controlled by an internal clock — a region in the hypothalamus of the brain called the suprachiasmatic nucleus (SCN)1.