Effects Of Early Life Stress On Behaviors And Methylation Of GABARAP Gene In The VTA Of Adult Rats

Objective:To investigate effects of early life stress on behaviors and methylation ofγ-aminobutyric acid type A（GABAA）receptor-associated protein（GABARAP）gene in the ventral tegmental area（VTA）of adult rats.Methods:The male litters of SD rats were randomly divided into maternal deprivation group（MD,N=18）and blank control group（C,N=20）after birth.The litters in the MD group were intervened by the maternal deprivation stress paradigm,and the litters in the blank control group were not given any experimental treatment.Rats were weaned and divided into cages at 21st days after birth（P21）.In adulthood（16 weeks of age）,the behaviors were evaluated by the open field test,the sucrose preference test,the forced swimming test,and the three-chamber social interaction test.The VTA brain tissue of rats was collected after the behavioral test.Bisulfite amplicon sequencing PCR was used to detect the methylation level of GABARAP in the VTA;real-time quantitative RT-PCR（RT-q PCR）was used to detect the m RNA expression level of GABARAP gene in the VTA;Western blot was used to detect the protein expression level of GABARAP,GABRG2 and Beclin1gene in the VTA.Results:1)Behavioral results:（1）The open field test showed that the vertical counts in the MD group were significantly lower than those in the C group（p<0.05）,but there were not significant differences in the total distance and the proportion of central distance between MD group and C group（p>0.05）.（2）The sucrose preference test showed that the sucrose preference rate in MD group was significantly lower than that in the C group（p<0.05）;（3）The forced swimming test showed that the immobility time in the MD group was significantly lower than that in the C group（p<0.05）,but there were not significant differences in the climbing time and the swimming time between MD group and C group（p>0.05）;（4）The three-chambe_IIr_I social interaction test showed no significant differences in the social interest index and social preference index between MD group and C group（p>0.05）.2)Biological results:The methylation level of GABARAP gene in the VTA of MD group rats was significantly higher than that of C group（p<0.05）;The m RNA expression level of GABARAP gene in the VTA of MD group rats was not significantly different from that in C group rats（p>0.05）;The protein expression levels of GABARAP,GABRG2 and Beclin1gene in the VTA of MD group rats were not significantly different from those in C group（p>0.05）.Conclusion:1)Early life stress can induce abnormal behaviors in adult rats,manifesting as reduced exploratory,anhedonia,and acute stress maladaptation;2)and increase the methylation level of GABARAP gene in the VTA,which may be involved in the pathological process of early life stress-induced abnormal behaviors.