Loss of responsiveness to melatonin in the aging mouse suprachiasmatic nucleus
Department of Neurobiology
Medical Subject Headings
Age Factors; *Aging; Animals; CREB-Binding Protein; Drug Interactions; Melatonin; Metallothionein; Mice; Mice, Knockout; Neurotransmitter Agents; Phosphorylation; Pituitary Adenylate Cyclase-Activating Polypeptide; Suprachiasmatic Nucleus
Neuroscience and Neurobiology
Melatonin modulates circadian rhythms via the hypothalamic suprachiasmatic nucleus (SCN). One of the most robust assays for SCN melatonin receptor activation in mice is the inhibition of PACAP-induced phosphorylation of the transcription factor Ca(2+)/cAMP responsive element binding protein (CREB). To assess the effect of aging on responsiveness to melatonin, SCN slices from mice of different ages were prepared and treated with PACAP alone or PACAP plus melatonin. CREB phosphorylation state was assessed by immunohistochemistry. In SCN slices from young (2-4-month-old) mice, melatonin reduced the level of phospho-CREB immunoreactivity following PACAP treatment in a dose-dependent manner. In SCN slices from aged mice (19-22 months of age), PACAP alone induced comparable levels of phospho-CREB, but melatonin treatment failed to inhibit the PACAP-induced CREB phosphorylation. The results indicate an age-related loss of sensitivity to melatonin in the SCN. The findings are discussed in the context of the impact of endogenous and exogenous melatonin on sleep in elderly humans.
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Citation: Neurobiol Aging. 2008 Mar;29(3):464-70. Epub 2006 Nov 22. Link to article on publisher's site