The Pacemaker in the Pituitary

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Science  22 Dec 2006:
Vol. 314, Issue 5807, pp. 1837m
DOI: 10.1126/science.314.5807.1837m

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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