Abstract
Daily restricted feeding (RF) causes a circadian rhythm even after SCN lesion, and the mechanism of this rhythm is poorly understood. Here, we examine the role of E-coupled breakfast oscillator in RF-entrained oscillation using Bmal1-luciferase transgenic mouse (gift from Honma, Hokkaido University). Circadian rhythm change of liver bioluminescence was recorded through Lumicycle after establishment RF oscillation. In SCN intact mice under LD cycle, daily RF applied during ZT0-4, ZT6-10, ZT12-16 or ZT18-22 for 1 week caused phase-advance of bioluminescence rhythm during ZT6-10 and phase-delay during ZT18-22. Interestingly, daily twice RF (ZT0-2 and ZT12-14) or (ZT6-8 and ZT18-20) did not caused phase change. This data suggests that daily twice RF is ineffective signal for entrainment under intact SCN. We did same experiment using SCN lesioned mice. These mice showed the clear bioluminescence rhythm in the liver, but its peak time was ranging from day to night. Daily RF for 4hrs entrained liver bioluminescence rhythm with a peak time (2 hrs after RF start time). Daily twice RF (2hrs with12-hr interval) also entrained liver bioluminescence rhythm with a peak time (2 hrs after former RF) when RF started at former clock time, and with a peak time (2 hrs after later RF) when RF started at later clock time. Thus, peak time was dependent on RF start clock time (breakfast time).In the present experiment, it is strongly suggested that fasting period is important for entrainment signal of RF-entrainment. [J Physiol Sci. 2008;58 Suppl:S13]
