title: Entrainment of the master circadian clock by scheduled feeding.
abstract: The master circadian clock, located in the mammalian suprachiasmatic nuclei (SCN), generates and coordinates circadian rhythmicity, i.e., internal organization of physiological and behavioral rhythms that cycle with a near 24-h period. Light is the most powerful synchronizer of the SCN. Although other nonphotic cues also have the potential to influence the circadian clock, their effects can be masked by photic cues. The purpose of this study was to investigate the ability of scheduled feeding to entrain the SCN in the absence of photic cues in four lines of house mouse (Mus domesticus). Mice were initially housed in 12:12-h light/dark cycle with ad libitum access to food for 6 h during the light period followed by 4-6 mo of constant dark under the same feeding schedule. Wheel running behavior suggested and circadian PER2 protein expression profiles in the SCN confirmed entrainment of the master circadian clock to the onset of food availability in 100% (49/49) of the line 2 mice in contrast to only 4% (1/24) in line 3 mice. Mice from line 1 and line 4 showed intermediate levels of entrainment, 57% (8/14) and 39% (7/18), respectively. The predictability of entrainment vs. nonentrainment in line 2 and line 3 and the novel entrainment process provide a powerful tool with which to further elucidate mechanisms involved in entrainment of the SCN by scheduled feeding.
authors.affiliation: Behavioral and Evolutionary Neuroscience Laboratory, Alaskan Basic Neuroscience Program, Institute of Arctic Biology, PO Box 757000, University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA. ffab@uaf.edu
authors.forename: Marina R
authors.initials: MR
authors.lastname: Castillo
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Hochstetler
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Tavernier
authors.forename: Dana M
authors.initials: DM
authors.lastname: Greene
authors.forename: Abel
authors.initials: A
authors.lastname: Bult-Ito
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001683:Biological Clocks / Q000502:physiology*; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism; D056950:Period Circadian Proteins; D013493:Suprachiasmatic Nucleus / Q000502:physiology*; D014157:Transcription Factors
chemical_list: D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D014157:Transcription Factors