| Circadian rhythm generally exists in most organisms, which is generated by an endogenic biological clock. In mammals, the circadian rhythms in behavior and physiology are regulated by a central pacemaker located in the suprachiasmatic nuclei (SCN) of the hypothalamus and many slave oscillators in peripheral tissues. The SCN clock is mainly regulated by the light cue whereas the peripheral clocks seem to be mainly entrained by the food signal. Previous studies on the peripheral clocks mainly focused on liver, heart and kidney etc. While studies on the digestive system out of the liver have rarely been reported. To understand how light and food cues might entrain the peripheral clocks involving the digestive system, we examined the effects of light and food signals on the expression of clock genes in the pancreas, duodenum and jejunum. Moreover, we also investgate the effects of vagotomy on the circadian regulation of peripheral clocks in digestive system of rats.Results obtained here indicated that the circadian expression of clock genes in digestive system were more sensitive to the food signal than the light signal, even though the individual reversal photoperiod has a certain effect on the circadian phase of clock genes. After reversing the feeding schedule, most of the clock genes in the jejunum finished their resetting within 7 days, while there were only part genes completely reset in the pancreas and duodenum. Moreover, the expression patterns of digestive enzyme genes were also changed by the individual reversal of photoperiod or feeding schedule.In addition, the sensitivity of circadian clock genes to the food stimuli was changed in the pancreas, duodenum and Jejunum after the blocking of the hepatic branch. More over vagotomy can significantly effects the expression level of digestive enzyme genes and the levels of digestive enzymes in the pancreas. Therefore, the vagus nerve can effectively regulate the function of circadian rhythm in digestive system. |
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