Daily restricted feeding resets the circadian clock in the suprachiasmatic nucleus of CS mice.
Circadian rhythms in clock gene expressions in the suprachiasmatic nucleus (SCN) of CS mice and C57BL/6J mice were measured under a daily restricted feeding (RF) schedule in continuous darkness (DD), and entrainment of the SCN circadian pacemaker to RF was examined. After 2-3 wk under a light-dark cycle with free access to food, animals were released into DD and fed for 3 h at a fixed time of day for 3-4 wk. Subsequently, they returned to having free access to food for 2-3 wk. In CS mice, wheel-running rhythms entrained to RF with a stable phase relationship between the activity onset and feeding time, and the rhythms started to free run from the feeding time after the termination of RF. mPer1, mPer2, and mBMAL1 mRNA rhythms in the SCN showed a fixed phase relationship with feeding time, indicating that the circadian pacemaker in the SCN entrained to RF. On the other hand, in C57BL/6J mice, wheel-running rhythms free ran under RF, and clock gene expression rhythms in the SCN showed a stable phase relation not to feeding time but to the behavioral rhythms, indicating that the circadian pacemaker in the SCN did not entrain. These results indicate that the SCN circadian pacemaker of CS mice is entrainable to RF under DD and suggest that CS mice have a circadian clock system that can be reset by a signal associated with feeding time.
Abe
Hiroshi
H
Department of Physiology, Hokkaido University Graduate School of Medicine, Sapporo, Japan. hiroabe@fmsrsa.fukui-med.ac.jp
Honma
Sato
S
Honma
Ken-Ichi
K
D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D031204:Caloric Restriction; D018797:Cell Cycle Proteins / Q000235:genetics; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology; D005260:Female; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics; D056950:Period Circadian Proteins; D013493:Suprachiasmatic Nucleus / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D014157:Transcription Factors; C538961:Bmal1 protein, mouse; C539023:Per1 protein, mouse; C513312:Per2 protein, mouse