The mammalian circadian clock is based on autonomous rhythmic expression of several clock genes in the pituitary gland, but how these signals are disseminated into the periphery remains unclear. In February 11 online Nature Neuroscience, Charlotte von Gall and colleagues from Johann Wolfgang Goethe-University, Frankfurt, Germany, show that rhythmic gene expression in the pituitary is linked with the release of the neurohormones melatonin and prolactin.

von Gall et al. used rodent pituitary cells and found that the cycling expression of the clock gene Period1 is dependent on the heterologous sensitization of the adenosine A2b receptor, which occurs through the nocturnal activation of melatonin mt1 receptors. In addition, they showed that when the impact of the melatonin is eliminated, the expression of Period1 is suppressed and caused the release of pituitary prolactin (Nat Neurosci 2002, DOI: 10.1038/nn806).

These results "expose a mechanism by which two convergent...

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