| PrefaceWith the development of modern society, the competition gradually become violent and life rhythm is increasingly fast, the incidence of depression further increase. After each recurrence, the coping capacity and life quality of person would descent and its social burden continuously increase. Especially its high risk of suicide is concerned extensively by people, therefore the mechanism of depression is paid more and more attention by scientist and doctor of medical field. The stressful events is an obvious factor to enhance the occurrence of depression , and the hippocampus of depression patients exit same appearance with rats after chronic stress. Therefore we can make animal model of depression by chronic stress to explore the pathogenesis of depression .Stress means a series of neuroendocrine response characterized with sympathetic excitation and excessive secretion of hypothalamus - pituitary - adrenal glands ( HPA) axis and further changes of function and metabolism . In the central nervous system ( CNS) , hippocampus is a vital area related with cognitive and behavioral function, which would be attacked easily by high level of glu-cocorticoid (GC) in stress for it possesses many glucocorticoid receptor ( GR). Brain -derived neurotrophic factor(BDNF) is a important member of neurotro-phins( NTs). BDNF has many effects ,it can enhance the connection of synapse and influence the neural plasticity and synthesis of neurotransmitters and neuro-trophins , also relate with long term potentiation(LTP) and learning and memory. In present study, we used the expression of BDNF as the marker of neural injury and protection to explore the neural changes in chronic stressful animal model . To study the relation between the expression of BDNF and the structural and functional changes of hippocampus , try to know the pathogenesis of depres-sion, and provide basis for etiological treatment and exploitation of new drugs for depression in clinic.Materials1, Experimental animals: Male Wistar rats weighting about 210 - 240g were purchased from the center of experimental animals in China Medical University.2, Experimental reagents: Rabbit anti - BDNF and SABC kit( Boster Biotechnology Co. LTD. )3, Experimental instruments: Electrophysiological apparatus , MetaMorph/ Cool Snapfx/Ax70 image analysis system.Methods1, Animal groupingExperimental rats were housed for 7 days to adapt the conditions of the lab. Then they were divided into experimental group and control group randomly , 12 rats and 8 rats respectively.2, Stress processExperimental group were fed separately one rat in one box. from 1 ~ 21 days, accept various types of stresses. The control group were fed in two boxes, four rats each box and no stress from 1 -21 days.3, Perfusion and SectionOn 22th day killed all the rats. Anaesthetized with 60mg/kg (i. p. ) of so-diumpentobarbital and perfused via left ventricle with 200ml Saline followed by 300ml 4% paraformaldhyde. Brains were removed and postfixed for more than 48 h. Then the brains were dehydrated through graded - concentration ethanol and embedded in olefin. And sections were cut coronally.4, Immunohistochemistry for BDNFUsed immunohistochemistry method to measure the expression of BDNF protein in hippocampus.5, image analysisTo select one sheet each rat to analyze CA1 CA2 CAS CA4 DG zone and calculate the sectional area (SA) and optical density (OD) of BDNF.6, statistical treatmentTo analyze the date with SPSS11.5 software.Results1, Weight and the results of Open - field testAfter 21 days stress, weight, ambulation, rearing and grooming decreased and stopping time in center, defecation increased in experimental group.2, Neurons under light microscopeCompared with control group , the neural distance between CA area and DG area increased and the amount of the neurons decreased in experimental group.3 , BDNF expression in hippocampusBDNF expressed obviously in CAS and DG area in control group and all sub - zon...
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