The Aggressive Changes In The Estrous Cycle Of Female Black Hamsters And The Differential Expression Of ERB In The Brain

Striped hamster(Cricetulus barabensis) is one of the dominant species of farmland rodents in northern China;the most important reason is its high reproductivity.During the reproductive process,female individuals need to devote a lot of time and energy on it;the purpose of behavior changes is to get closer to the male so that it can achieve the mating to propagate the genes to the next generation.In order to enhance the competitiveness and better mating with suitable male individuals,the aggression of female striped hamster changed in different stages of estrous cycles.Therefore this ecological optimization strategy is closely related to finding a mate and reproduction.Meanwhile,Estrogen and its receptors especially the ERB expression in the hippocampus of the brain plays an important role in the progress of rodents’ estrus.Through studying the correlations between ERB expression in the brain of female striped hamster and behavior changes in estrous cycle,we can have a deeper insights in the internal mechanism and get further understanding of striped hamster on its behavioral characteristics and life history strategies.We monitored the estrous cycle of wild caught female striped hamsters then determined the experimental time points at different stages.Next the Handling-bag experiment and the Neutral arena experiment were performed in order to study the change of behavior characteristics through resting metabolic rate(RMR)detection.Then we used the QRT-PCR to study the expression of ERB in the brain of female striped hamster which were killed in different estrous stages,at the meanwhile,the concentration of estrogen in the blood was measured.The results show that:1.The most severe aggressive performance was shown in proestrus,and less aggressive performance was noticed in the estrous period,and the least one was identified in the estrous and metestrus,when the female striped hamster were captured outside or were fighting.In the proestrus.The most increased aggressive behavior includes threat and boxing which are named as the basic aggressive behavior.2.When staying with male individuals,aggressive performance was more severe in proestrus,estrous and metestrus except in the estrous;most significant social behavior was identified in estrus.3.The amount of ERB in the brain of female striped hamster was lower during the proestrus,and higher in metestrus and dioestrus which was negatively related with There was a significant negative correlation Handling-bag time(r=-0.731,P<0.01)and the frequency of same-sex encounters(r=-0.813,P<0.01).4.The level of RMR and estrogen in the blood was much higher in the estrous period offemale striped hamster and there was a linear positive correlation between them(r=0.728,P<0.01).As a conclusion: There are significant differences in the aggressive behavior of female striped hamsters at different stages of the estrous cycle.Trapped pressure or fighting with the same sex and staying with male all have a certain impact on its behaviors.ERB has a certain regulatory role in female striped hamster’s behavior,but there are differences in the effects of different stages of estrous cycle.Striped hamsters in proestrus will exhibit more aggressive when face to external pressure or capture same-sex competitors in order to ensure the normal reproductive process.But for reducing energy consumption,most increase of aggressive behaviors are basic aggressive behavior,females will not allow the male come close except in estrus,which consistent with the characteristic of being solitary rat;the expression of ERB in female striped hamster’s brain has inhibition to aggressive behavior;it maintain a high metabolic rate and high blood levels of estrogen during the estrous period,representing the female striped hamsters allocated more energy to the breeding activity.This study is helpful to have a deeper understanding about the brain mechanism of animal behavior regulation.Also,it is helpful to understanding of the behavior mechanism and life history strategy in the process of reproduction of striped hamster.Meanwhile,these findings provide more experimental basis for the reproductive regulation of striped hamster study.