The effects of feeding after fasting on the circadian clock in CS mice

点击翻译按钮获取中文摘要

Circadian clock in the SCN (suprachiasmatic nucleus) of CS mice (an inbred strain) is entrained by RF (restricted feeding schedule) unlike other strains of mice and rats. To clarify the mechanism of RF-entrainment in the CS mice, present study examined whether feeding after fasting resets the phase of circadian rhythm of CS mice.1. Laboratory for mouse circadian rhythm research was established in Division of Psychology, Faculty of Medical Sciences, University of Fukui.2. Daily food intakes of CS and C57BL/6J mice were measured under ad lib feeding and light-dark condition (LD). There was no difference in the mean daily food intakes between CS and C57BL/6J mice.3. Each mouse was housed in a running wheel cage and measured the activity rhythm under LD followed by constant darkness (DD). In the 2nd day of DD, food were deprived at one of 6 phases (ZT2, 6,10,14,18 and 22 ; ZT=Zeitgeber time, ZT12=dark onset of LD) and returned to the cage after 24 hours. The single feeding after 24-hour food deprivation at all 6 phases induced no changes in the behavioral rhythms in both CS and C57BL/6J mice.4. In the CS mice, clock gene mRNAs in the SCN and other brain areas at 2 hours after feeding following the 48-hour food deprivation. The single feeding after food deprivation induced no changes in the mPerl and mPer2 mRNAs in the SCN, while it significantly increased mPerl and mPer2 mRNAs in other brain areas.5. These results suggest that the RF-entrainment of CS mice is not regulated by the phase-resetting effect of single feeding stimulus on the circadian clock in the SCN, and that the clock genes in other brain areas might play a role in the regulation of behavioral rhythm under feeding after fasting.