My laboratory studies the molecular and neural basis of endogenous daily (circadian) rhythms in mammals. We focus upon the suprachiasmatic nucleus of the hypothalamus (SCN), a master pacemaker critical not only to general activity rhythms but also to the estrous cycle, the rhythmic secretion of many hormones, and seasonal breeding. The restriction of reproduction to a particular time of year depends upon the discrimination of daylength. The circadian system accomplishes this by SCN-regulated secretion of the hormone melatonin by the pineal gland, and detection of melatonin duration using highly specific cell membrane receptors in the brain.

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