Clock gene response against skelton type entrainment stimulation in mice

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The aim of this experiment is to elucidate the mechanism of skeleton-type photic and non-photic entrainment like food entrainment in mice. First we examined the circadian pattern of clock gene expression in the liver under one-hr light stimulation in the morning and one-hr light stimulation in the evening. This lighting schedule could entrain the locomotor activity rhythm and also liver dock gene expression rhythm. Thus, skeleton lighting schedule can entrain the circadian dock just like usual 12-hr light-dark schedule. Next, we examined the circadian pattern of clock gene expression in the liver under 2-hr feeding in the morning and 2-hr feeding in the evening. This feeding schedule could entrain the liver clock gene expression rhythm, and its pattern was very similar to adlib feeding group. Thus, two feeding times per day with morning and evening could entrain the peripheral circadian rhythm. In the third experiment, we changed the ratio of feeding volume in the morning and evening. If the more feeding volume was applied in the morning, there was little effect on the phase of dock gene expression. However, if the more feeding volume was applied in the evening, phase of dock gene expression rhythm was strongly delayed. Taken together these results suggest that food intake in the morning is important to keep the phase of dock gene expression the peripheral organs.