The Effect Of Early Life Chronic Stress On Aggressive Behavior And Relative Brain Zone In Puberty Rats

OBJECTIVETo explore the effects of early life chronic stress on aggressivebehavior and relative brain zone (prefrontal cortex, hypothalamus andamygdala) in puberty rats.METHODS1Sixty Male SD rats are randomly divided into three groups(n=15):(1)experimental group: Early life chronic stress for5weeks.①socialinsolation②n on-reward③s ocial instigation④r esident-intruder (2) normalaggresssion group: only resident-intruder;(3) control group: fed normally(5rats/cage), the others were the intruders.2Behavior test2.1Aggressive behavior test (resident-intruder test and neutral areatest)(1) Total aggressive times: bite (times)+mounting (times)+aggressivegrooming (times)+aggressive chasing (times)(2) Latency time of attack: the time from beginning (remove wire mesh) to attack(3) The total time of attack: the time during attack(4) The ratio of attack and threat (A/T)(5) attack the vulnerable parts(head/abdomen/throat)(6) persistence attack after intruder displays submissive2.2anxiety and depressed test (the open field test)3Biological test3.1Tunel (TdT-mediated dUTP nick end labeling): to observe theneuron apoptosis of prefrontal cortex, hypothalamus and amygdala afterearly life chronic stress.3.2Electron Microscope: to observe the neuron apoptosis of prefrontalcortex, hypothalamus and amygdala and ultra microstructure of synapsis.RESULTS1Behavioral test: After early life chronic stress, the aggressive ofexperimental group in puberty were significantly higher than in othergroups (p<0.01). Resident-intruder test: there were significant differencesamong experimental group[(90.93±7.51) times], normal aggresssiongroup[(16.47±4.12) times] and control group[(5.00±3.09) times](p<0.01).The abnormal aggressive mode appeared in the experimental group. Forexample, the experimental group showed persistence attack after intruderdisplays submissive and attack the vulnerable parts, and its aggressive stillwere significantly higher than in other groups(p<0.01). The experimental group didn’t show obvious anxiety and depression.2Biological test: In tunel test, the apoptotic neuron level ofexperimental group were significantly higher than in other groups (p<0.01).In electron microscope, the number density and square density ofexperimental group were significantly lower than in other groups inprefrontal cortex (p<0.01). But there weren’t significantly differencesamong three groups in hypothalamus and amygdala(p>0.05).CONCLUSIONS1The aggressive behavior of puberty rats is in accord with standardsof animal violence after several kinds of early life chronic stress.2The neuronal apoptosis and ultra microstructure of synapsis inprefrontal cortex of puberty rats are abnormal after several kinds of earlylife chronic stress.3The neuronal apoptosis and ultra microstructure of synapsis inhypothalamus and amygdala of puberty rats are not obvious abnormal afterseveral kinds of early life chronic stress.These results suggest that several kinds of early life chronic stresscause disinhibition in hypothalamus and amygdala by damage prefrontalcortex, and resulting in violence.