| The incidence of depression is increasing year by year. It is threating to human' s health, and has made people pay attention to it. In the past, the study of pathogenesis of depression was limited to the changes of neurotransmitters at the synapse. By now, studies have confirmed that the function and structure of the hippocampus has changed in the depression. Furthermore , studies indicated that the apoptosis of the hippocampus was related to those changes. However, the study about neural apoptosis was mainly concerntrated on cerebral ischemia or anoxia of brain. Tlie reports about neural apoptosis in depression was few. So , it is important to study the relationship between the stresses and hippocampal apoptosis, which was studied in present experiment through rat models of depression induced by chronic stresses.Materials1. Subject; Aldut male Wistar rats (n =20) (Animal institute of CMU) weighing about 200g were used.2. Experimental reagents; rabbit anti - Bel - xl, SABC kit, TUNEL kit.3. Instruments; Electrophysiological apparatus, Meta Morph/Cool Snapfx /Ax70 image analysis system.MethodsAnimals were observed in open - field test and were allowed at least one week to acclimatize to the housing conditions before the beginning of experiment. Rats were randomly divided into 2 groups. Group B (n = 5 ) served as normal control. Group A ( n = 15 ) received 21 - day chronic stress. The control group were housed five per cage with ad libitum access to food and water. The stress group were housed individually. The stress group were exposed to a schedule of different daily stressors. The elements of the schedule included; shock stress; food deprivation; forced swimming; water deprivation; heating stress; tottering; clamping tail.At the 22nd days, all animals were killed by transcardial perfu-sion. Then, the rats were decapitated, after which, the brain were removed into 4% formaldehydum polymerisatum.TUNEL method was used to measure the hippocampal apoptosis. Immunohistochemistry method was used to measure the expression of Bcl xl in the hippocampus.Statistical analysis was carried out with SPSS10.0ResultsOpen field measures showed that stopping time in the centre of group A increased compared with group B (P <0.01). Ambulations, rearings and groomings of group A were significant decreased compared with group B ( P < 0. 01). Defecation of group A was significant increased ( P < 0.01).The difference of weights between group A and group B is signifi-cant. After 21 -day chronic stress, the weights of group A decreased significantly compared with the group B (P <0.01).The percent of positive cells in the hippocampus of group A increased compared with group B in the TUNEL method ( P < 0. 01). The difference of the percent of positive cells in the subregion of hippocampus was significant between group A and group B. That of group A increased compared with group B (P <0.01).In the immunohistochemistry method, the result was just reverse. The percent of positive cells in the hippocampus of group A decreased compared with group B (P <0.01). The difference of the percent of positive cells in the subregion of hippocampus was significant between group A and group B. That of group A decreased compared with group B (P <0.01).DiscussionHow to evaluate a model of depression mainly depends on the behavioral changes of the animal. The open field test is used to reflect the behavioral changes of the animal. In our study, the rats endured chronic and comprehensive stress showed decreasing activities. That is similar to the symptom of depression, which indicated the rat models of depression were made successfully.It has been confirmed that the chronic stress could induce depression in our study. Why could the stress cause depression By now, studies have demonstrated that stress could injure the hippocampus and induce the depression, and many people thought the neural apop-tosis be involved in the damage of hippocampus. But it is under debated now.In our...
|
PDF Full Text Request