title: Feeding melatonin enhances the phase shifting response to triazolam in both young and old golden hamsters.
abstract: Aging alters many aspects of circadian rhythmicity, including responsivity to phase-shifting stimuli and the amplitude of the rhythm of melatonin secretion. As melatonin is both an output from and an input to the circadian clock, we hypothesized that the decreased melatonin levels exhibited by old hamsters may adversely impact the circadian system as a whole. We enhanced the diurnal rhythm of melatonin by feeding melatonin to young and old hamsters. Animals of both age groups on the melatonin diet showed larger phase shifts than control-fed animals in response to an injection with the benzodiazepine triazolam at a circadian time known to induce phase advances in the activity rhythm of young animals. Thus melatonin treatment can increase the sensitivity of the circadian timing system of young animals to a nonphotic stimulus, and the ability to increase this sensitivity persists into old age, indicating exogenous melatonin might be useful in reversing at least some age-related changes in circadian clock function.
authors.affiliation: Department of Neurobiology and Physiology and Center for Sleep and Circadian Biology, Northwestern University, Evanston, Illinois 60208, USA. kolkerd@mail.nih.gov
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Kolker
authors.forename: Susan
authors.initials: S
authors.lastname: Losee Olson
authors.forename: Jeanette
authors.initials: J
authors.lastname: Dutton-Boilek
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Bennett
authors.forename: Edward P
authors.initials: EP
authors.lastname: Wallen
authors.forename: Teresa H
authors.initials: TH
authors.lastname: Horton
authors.forename: Fred W
authors.initials: FW
authors.lastname: Turek
mesh_terms: D000284:Administration, Oral; D000375:Aging / Q000502:physiology*; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D006224:Cricetinae; D004357:Drug Synergism; D066298:In Vitro Techniques; D008297:Male; D008550:Melatonin / Q000008:administration & dosage* / Q000494:pharmacology; D008647:Mesocricetus; D012016:Reference Values; D014229:Triazolam / Q000494:pharmacology*
chemical_list: D014229:Triazolam; D008550:Melatonin