Daily Rhythm Of The Physiology,Behavior And The Expression Of Per1 In The Djungarian Hamster(Phodopus Sungorus) Regulated By Photoperiod

Biological rhythm is a time period phenomenon,formed by organisms in order to adapte to the environment.Daily rhythm is an important biological rhythm and exists in almost all living organisms from single-cell organisms to humans.Photoperiod is the main environmental factor that regulates the daily rhythm of animals,and the daily rhythm is also regulated by clock genes in organisms.Per1 is the main clock gene regulating the daily rhythm of the animals.The Djungarian hamster has the characteristics,such as moving slowly,higher fertility,rearing simply,easy to be caught.The Djungarian hamster is sensitive to the photoperiod,and could be used as an experimental animal model to study the animal physiology and behavior regulated by photoperiod.The Djungarian hamsters were fed under long photoperiod(16L:8D,LD)and short photoperiod(8L:16D,SD)respectively for 30 days in this experiment.The daily rhythm of the physiology and behavior of the Djungarian hamsters,the partial cDNA sequence of Per1 in the Djungarian hamsters and the daily expression rhythm of Per1 in the hypothalamus of the Djungarian hamsters were studied to explore the effects of Per1 on the daily rhythm of the physiology and behavior in the Djungarian hamsters.The results showed that significant differences existed in physiology,behavior and expression levels of Per1 in the hypothalamus between individuals from LD and SD conditions(P<0.05).Physiological results showed that the resting metabolic rates of the Djungarian hamsters at 4,16 and 20 o'clock were significantly different between individuals from different photoperiods(P<0.05).At 24 o'clock,the resting metabolic rates dividuals from SD had significantly higher total moving distances than from LD conditions(P< 0.01)and no significant differences were detected at other time points(P>0.05).The results indicate that photoperiod may play an important role in regulating the daily rhythm of physiology in animals.Behavioral results showed that:(1)Central moving distance.Significant difference were detected between LD and SD at 12 and 20 o'clock(P<0.05).At 4 o'clock,the central moving distance were significantly different between the Djungarian hamsters from LD and SD at 0.01 level,and no significant difference exist at other time points(P>0.05);at 4 o'clock,the central moving distances of the LD individuals were significantly higher than that of SD individuals;at12 and 20 o'clock,the central moving distances were significantly higher in the Djungarian hamsters from SD than that from LD.(2)Total moving distance.At 8 o'clock,the total moving distances were significantly higher from the Djungarian hamsters treated with SD than with LD(P<0.05);At 20 o'clock,the individuals from SD had significantly higher total moving distances than from LD conditions(P< 0.01),and no significant difference existed at other examined timepoints(P>0.05).(3)Central activity.At 8 o'clock,the central activity of the Djungarian hamsters under SD conditions was significantly higher than that of the LD condition(P<0.05).At 4o'clock,the central activity of the Djungarian hamsters under LD conditions It was significantly higher than the central activity under SD conditions(P<0.01),and no significant differences were detected at other time point.(4)Total activity.At 8 o'clock,the total activity of individuals under SD conditions was significantly higher than that of LD(P<0.05).At 20 o'clock,the total activity of individuals under SD conditions was significantly higher than that of LD(P<0.01),and no significant difference existed at other examined time.(P>0.05).(5)Central activity time.The Djungarian hamsters had significantly longer central activity time from SD than from LD at 12o'clock,and at other examined time point,no significant differences were detected(P>0.05).Therefore,the activity,activity distance and activity time of the Djungarian hamsters were affected by the photoperiod,which suggests the behavior of the Djungarian hamsters is affected by photoperiod.In this study,partial cDNA sequence of Per1 of the Djungarian hamsters was cloned and includes 897 bp,encoding 297 amino acids.The homology comparison results showed that the rodents including Phodopus sungorus,Cricetulus Barabensis,Mus musculus and Rattus norvegicus are closely related,while the rodents have farer relationship with the primates and ungulates,which is similar to traditional species classification.The results suggest that Per1 is conservative during evolution process,and also proved the cDNA sequence cloned in this study is correct.The real-time quantitative PCR results showed that:(1)At 8,16 and 20 o'clock,significant differences of the relative expression levels of Per1 were detected between the individuals from LD and SD(P<0.05).At 24 o'clock,the relative expression levels of Per1 were significantly different between the Djungarian hamsters from LD and SD at 0.01 level.(2)At 4,8,16 and 20o'clock,the relative expression levels of Per1 of the Djungarian hamsters from LD conditions were significantly higher than that from SD individuals(P<0.05);At 24 o'clock,the Djungarian hamsters from SD conditions had significantly higher relative expression levels of Per1 than that from LD conditions(P<0.05).(3)For the Djungarian hamsters from LD conditions,the highest expression level of Per1 exist at 4 o'clock,and the lowest at 20 o'clock;while the individuals from SD conditions had the highest expression level of Per1 at 24 o'clock and the lowest at 16o'clock.The results suggest that the relative expression level of Per1 in the hypothalamus of the Djungarian hamsters is affected by the photoperiod,which indicates that the photoperiod affects the daily rhythm of Per1 expression in the hypothalamus of the Djungarian hamsters,and then regulates the physiology and behavior of the animals.In summary,this study explored the daily rhythm of the physiology,behavior and the expression of Per1 in the hypothalamus of the Djungarian hamsters regulated by the photoperiod.The results lay foundation to explore the role of Per1 in regulating the physiology and behavior of the animals,and had important theoretical implication.