| Background: Emotion is very important in the psychological development of human.It is closely related with learning and memory, character and temperament. It willbe good for our development of intelligence, sentiment and the ability to adaptthe society, and also good for our physical and mental health. The are more andmore psychological problems with children, which seriously influence their lifeand learning, even make them have trouble in mental health and commit a crime. Thereare many complicated reasons in the development of mental problems, including theability of emotion and character. Early life stress seriously influences thedevelopment of character and the ability of behavior. The molecular mechanismsof emotion is not clearly now. But materials from the research of emotional disorderindicate that the disfunction of monoamine nervous system, the excess activationof Hypothalamic-Pituitary- Adrenal axis(HPA) and the excess expression ofinflammatory cytokines may participate the course of emotional disorders. Manyclinical and epidemic researches indicate that Early life stress significantlyincrease the incidence of emotional disorders. Although there are more and moreresearches on the biological mechanisms of emotional disorders, we still knowlittle. There are many kinds of reports on the change of 5-Hydroxytryptamine (5-HT)and its recepter in brain after stess, including enhancement and inhibition, whichare related with the kind, intensityand time of stress. There are also differentchanges in diferent region of the brain. The 5-HT system is complicated associatedwith HPA and other nervous information transmission, and also closely relatedwith emotion. So 5-HT system is thought to be important mediated material inpsychiaty caused by stress. The present study try to construct early lif stressmodel of rat, and then find the biological mechanisms of the influence of earlylif stress on the learning and memory, emotion ability after adult.Study one: Objective: Consruct a early life stress model,through the maternaldeprivation(MD), Locomoter Test and Shuttle Box Test. Obeserbe the influnece ofearly life stress on the behavior and 5-HT1A recepter in CA1 of hippocampus ofrats after adult.Materials and Methods: Newborn male Sprague-Dawley(SD) rats are divided intotwo groups: (1)MD group(38): MD for 1 hour every day from PND (post newborn day)2-21. (2)control(N)group(20): normal rearing after born. Observe the behaviour(locomotor an learning) of adult rats (2-month-old) after MD and the expressionof 5-HT1A recepter in CA1 of hippocampus. The data is analyzed by the softwareExcel 2000 and SPSS 11.0, using T-test.Results:1. There are no differences between MD group and control group in totaldistance, rest time, central distance and peripheral distance in LocomotorTest(P＞0.05). This result indicates that there are no difefences between MD grouprats and control group rats in lomotor afer adult. 2. There are no differencesbetween MD group and control group in Shuttle Box Test(P＞0.05), indicating thatthere are no difefences between MD group rats and control group rats in learningand memory after adult.3. The result of immunohistochemistry show that the positive cell of 5-HT1Arecepter mainly distribute in CA1 of hippocampus. But there are no diference betweenMD group rats and control group rats in the expression of 5-HT1A recepter in CA1of hippocampus(P＞0.05).Study two:Objective: give the MD guoup rats and control rats chronic stress after 2 months,in order to observe the long-term influnece of early life stress on the behaviorand 5-HT1A recepter in CA1 of hippocampus of rats after adult.Naterials and Methods: 2-month-old MD group rats and control group rats areboth divided into two groups:(1)chronic stress group:give the rats chronic stressfor 10 days. (2)control group:normal rearing. So there are totally 4 groups:MD+chronic stress(MD+S), MD+control(MD+C), control+ chronic stress(N+S), control+control(N+C). Observe the behaviour (locomotor an learning) of adult rats(2-month-old) after MD and the expression of 5-HT1A recepter in CA1 of hippocampus.The data is analyzed by the software Excel 2000 and SPSS 11.0 , using T-test andANOVA.Results: 1. MD+S group shows significant decrease in total distance(P＜0.001),increase in resting time(P＜0.01), decrease in central distance(P＜0.01),compared with MD+C. N+S group shows significant decrease in total distance(P＜0.001), increase in resting time(P＜0.01), decrease in central distance(P＜0.01),compared with N+C. MD+S shows decrease in total distance(P＜0.001), decrease incentral distance(P＜0.01), increase in resting time(P＜0.01), compared withN+C. These results indicating that chronic stress can depress the locomotor of rats,and early life stress can reinforce the depression of chronic stress. 2. MD+S groupshows decrease in learning and memory in Shuttle Box Test (P＜0.05), comparedwith MD+C. N+S group shows decrease in learning and memory in Shuttle Box Test(P＜0.05), compared with N+C. MD+S shows decrease in learning and memory inShuttle Box Test, compared with N+S. These results indicating that chronic stresscan depress the ability of learning and memory of rats, and early life stress canreinforce the depression of chronic stress. 3. MD+S group shows decrease inexpression of 5-HT1A recepter in CA1 of hippocampus (P＜0.05), compared with MD+C.N+S group shows decrease in expression of 5-HT1A recepter in CA1 of hippocampus(P＜0.05), compared with N+C. MD+S shows decrease in expression of 5-HT1A recepterin CA1 of hippocampus (P＜0.05), compared with N+S.Conclusions: Chronic stress can make Maternal deprivation rats beheaviourdepression and deceasing in learning and memory, decreasing expression of 5-HT1Arecepter in CA1 of hippocampus. Maternal deprivation is one of the importantreasons in the change of beheavior of rats, and decrease in expression of 5-HT1Arecepter in CA1 of hippocampus may be one of the mechanisms. |
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