title: Constant light induces alterations in melatonin levels, food intake, feed efficiency, visceral adiposity, and circadian rhythms in rats.
abstract: Melatonin levels, metabolic parameters, circadian rhythm activity patterns, and behavior were observed in rats subjected to a 12-h/12-h light/dark cycle (LD) compared to animals exposed to continuous dark (DD) or continuous light (LL). LD and DD animals were similar in melatonin levels, food intake, relative food intake, feed efficiency, water intake, circadian activity levels, and behavior. LL animals had lower melatonin levels in the subjective dark compared to LD and DD animals. Food intake, relative food intake, and water intake values were lower and feed efficiency was more positive in LL animals compared to LD and DD animals. In addition, LL animals exhibited greater visceral adiposity than the other two groups. The circadian rhythmicity of activity became free-running in LL animals and there was a decrease in overall activity. Notable behavioral changes in LL animals were an increase in irritability and excitability. Results indicate that a decrease in melatonin levels and concomitant changes in metabolism, circadian rhythms, and behavior are consequences of exposure to constant light.
authors.affiliation: Department of Biology, John Carroll University, 20700 North Park Blvd., Cleveland, OH 44118, USA. cwideman@jcu.edu
authors.forename: Cyrilla H
authors.initials: CH
authors.lastname: Wideman
authors.forename: Helen M
authors.initials: HM
authors.lastname: Murphy
mesh_terms: D000223:Adaptation, Psychological / Q000528:radiation effects*; D050154:Adiposity / Q000528:radiation effects*; D000465:Algorithms; D000818:Animals; D001835:Body Weight / Q000528:radiation effects; D002940:Circadian Rhythm / Q000528:radiation effects*; D004326:Drinking / Q000528:radiation effects; D004435:Eating / Q000528:radiation effects*; D050152:Intra-Abdominal Fat / Q000528:radiation effects; D008027:Light / Q000009:adverse effects*; D008297:Male; D008550:Melatonin / Q000097:blood / Q000378:metabolism*; D009043:Motor Activity / Q000528:radiation effects*; D051381:Rats; D020318:Rats, Long-Evans; D012892:Sleep Deprivation; D013686:Telemetry; D013997:Time Factors
chemical_list: D008550:Melatonin