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Science 22 December 2006:
Vol. 314. no. 5807, p. 1837
DOI: 10.1126/science.314.5807.1837m
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This Week in Science

Endogenous annual rhythms drive many long-term cycles in physiology and behavior in long-lived vertebrates, but the anatomical and cellular basis of such rhythm generation remains a mystery. Lincoln et al. (p. 1941) analyzed prolactin secretion and its associated biological changes in sheep whose pituitary gland had been surgically disconnected from the central nervous system. Melatonin secretion by the pineal gland regulated the hormonal effect. Timer cells in the pituitary possess melatonin receptors that permit their regulation by the duration of the melatonin signal. These timer cells, in turn, drive the prolactin synthesizing and secreting cells, which themselves lack melatonin receptors.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)