Effects Of Mate Isolation On Social Behavior And Dopamine Receptor Expression In Related Brain Regions In Midday Gerbil(Meriones Meridianus)

As a relatively stable breeding strategy,mating system is the result of long-term mutual adaptation between animals and the environment,and changes with the change of environmental conditions.Monogamous prairie voles(Micrtus ochrogaster)have long-lasting and stable mating relationships.However,the stress caused by the disruption of mating relationships after the formation of mating relationships can have adverse effects on social behavior and endocrine secretion.For example,social isolation can lead to anxious or depression-like behavior,changes in blood corticosterone levels,and changes in dopamine receptor expression.And dopamine plays a crucial role in the formation and maintenance of relationships.In the Nucleus accumbens(NAc)Nucleus accumbens,the dopamine ? receptor(D1R)and dopamine ? receptor(D2R)in the process of spouse relationship formation plays an opposite role: the prairie vole NAc D2 R activation in promoting the formation of spouse relationship,and activate the D1 R is to prevent the formation of spouse relationship.Spousal breakdown can adversely affect emotional and social behavior in animals,but the effect on dopamine receptors in related brain areas is unclear.Midday gerbil(Meriones meridianus)is an agricultural pest in desert and semi-desert areas of northern China.It has strong adaptability and is harmful to desert plants and sand-fixing plants.Laboratory studies show that the rat is a good zoological model for studying social behavior because of its mild disposition and rich social behavior.For example;The young of the gerbil showed high level of ultrasonography and the male gerbils showed high level of paternal behavior.The results of individual microsatellite analysis of the gerbil population in natural habitat showed that there were a variety of genetic mating systems in the gerbil population in minqin desert area.In this study,the experimental gerbils of F1 generation bred in the laboratory were taken as the research objects,and the experiment was started at the age of 90-110 days.The experiment was divided into the following four groups: FF: the female-female control group,MM: the male-male control group,FMP: the female-male paired group,and FMI:The group of female-male paired who were isolated after 10 days of cohabitation.After 10 days of pairing,social interaction experiments were carried out in FMP group,FF group and MM group respectively to explore the influence of different pairing experiences on social behaviors of gerbils at meridian.After 10 days of pairing,they were isolated for 3days.Social interaction experiments were conducted in FMP group and FMI group respectively to explore the influence of isolation on the social behavior of male and female paired individuals.After the behavioral experiment,the expression of D1 R and D2 R in relevant brain regions was investigated by Western Blot.The BSP methylation levels in D1 R and D2 R gene promoter regions were investigated.The main results are as follows:1.Social interaction test(SIT): After 10 days of pairing,compared with MM group,both male and female gerbils in the FMP group had significantly reduced defensive behaviors and significantly increased mutual exploration(intimacy)behaviors,indicating that male and female pairing increased the intimate behaviors between male and female individuals.After 13 days of mating,compared with the FMP group,both male and female individuals in the FMI group showed an increase in frequency and time of defensive behaviors,and a decrease in exploratory behaviors,indicating that social isolation during the formation of spousal relationship significantly damaged the intimate behaviors between male and female individuals.2.Western Blot: Compared with FF group,the expression level of D1 R in NAc of females in FMP group was increased,which may be related to the maintenance of post pairing relationship.Compared with the FF group,the expression level of D2 R protein in the five brain regions of m PFC,NAc,CP,VTA and SN was increased in the FMP group,indicating that the expression of D2 R was related to the pairing of midday gerbil.Compared with the MM group,the expression level of D1 R in the m PFC and CP brain regions was increased in the FMP group,which may be related to the maintenance of mate relationship.Compared with MM group,the expression level of D2 R in CP and VTA brain regions of males in FMP group was increased,which may be related to the formation of mate bond and the increase of intimate behavior.Compared with the FMI group,the expression of D1 R in m PFC and NAc was increased in the FMP group,which may be related to the decrease of intimate behavior between partners caused by social isolation.Compared with females in the FMI group,the expression of D1 R in the m PFC brain region of females in the FMP group was increased and D2 R was decreased,indicating that D1 R and D2 R had opposite effects in the spousal isolated midday gerbil.Compared with the FMI group,the expression of D2 R protein in the five brain regions of m PFC,NAC,CP,VTA and SN was also increased in the FMP group,indicating that mate isolation was negatively correlated with the expression of D2 R.Compared with the FMI group,the expression level of D1 R in the m PFC brain region of males in the FMP group was decreased and D2 R was increased.There may be gender differences in the expression of dopamine receptors in the m PFC brain region between males and females.3.Methylation experiment: The 913 bp sequence of D1 R of gerbils was sequenced,and its homology with its relative species,long-claw gerbils,was 96.79%.The 1016 bp sequence of D2 R of gerbils at noon was 95.83% homology with long-claw gerbils.The Cp G island fragment in the D1 R promoter region was 206 bp in length and contained 8Cp G loci.The position in the sequence is 29,41,69,111,130,135,162,183.The Cp G island fragment in the D2 R promoter region was 204 bp in length and contained 13 Cp G sites.The position in the sequence is 37,52,70,82,94,127,134,140,143,149,164,172,175.The methylation degree of D1 R promoter was 7.76% in male meridional gerbils and 12.74% in D2 R promoter.In this study,only the feasibility of DAR DNA promoter methylation was verified,and the sample size was small.Therefore,no other conclusions were drawn except the D1 R and D2 R DNA sequences in gerbils.