title: Loss of responsiveness to melatonin in the aging mouse suprachiasmatic nucleus.
abstract: 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.
authors.affiliation: Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA. vongall@med.uni-frankfurt.de
authors.forename: Charlotte
authors.initials: C
authors.lastname: von Gall
authors.forename: David R
authors.initials: DR
authors.lastname: Weaver
mesh_terms: D000367:Age Factors; D000375:Aging; D000818:Animals; D050882:CREB-Binding Protein / Q000378:metabolism; D004347:Drug Interactions; D066298:In Vitro Techniques; D008550:Melatonin / Q000378:metabolism / Q000494:pharmacology*; D008668:Metallothionein / Q000172:deficiency; D051379:Mice; D018345:Mice, Knockout; D018377:Neurotransmitter Agents / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000494:pharmacology; D013493:Suprachiasmatic Nucleus / Q000187:drug effects* / Q000378:metabolism
chemical_list: D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; C525355:metallothionein-1, mouse; D008668:Metallothionein; D050882:CREB-Binding Protein; D008550:Melatonin