Abstract
To explain to entrain seasonal day length change, there is a model of two separate circadian oscillators in SCN of nocturnal rodents: an E oscillator, which entrain to the sunset, and M oscillator, which entrain to dawn. It is thought that two oscillators regulate onset and offset of activity rhythm respectively. It turns out that these oscillators separate under specific LD conditions (DLDL5:7:5:7, LD18:6 etc), and mPer1 expression shows bimodal rhythm then in a whole SCN. At this time, the role to regulate the peripheral tissue of E/M oscillator is examined by observing the rhythm of clock gene expression of the mouse liver. We investigated the rhythm of liver through Lumicycle using Bmal1::luciferase and Per1::luciferase transgenic mice which were housed individually in cage equipped with running wheel under the specific LD conditions. Even when the bimodal rhythm was formed in SCN, unimodal rhythm was always formed in liver. Moreover, the phase of this rhythm was preferred to be entrained mainly by E oscillator. Since the feeding rhythm is thought to be used as the major factor to form circadian rhythm in the liver, we considered that feeding start by switch-on of E oscillator deliver some information to reset the liver clock. [J Physiol Sci. 2008;58 Suppl:S86]
