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Objective: Accompanying with the sex behavior impairment, clinical and basic research indicates that chronic stress can lead to emotional disease and reproductive damage. In this study, combining with isolation, we use chronic unpredictable mild stress to establish the chronic multiple stress model of rats. By used this model, the effects of chronic stress on rat’s emotions, sex behavior and function of testicular are detected. And then, the mechanism of the effects of chronic stress on reproductive behavior and reproductive functions are explored.Methods: Male Sprague-Dawley rats were randomly divided into two groups, control group and stress model group (n=8). Combining with isolated raised, the model group was given 35 days of chronic unpredictable mild stress, while the control group was normal fed. We observed the two groups’body weight during experiment process, used the Open-field test and the sugar water consumption to evaluate the changes of emotional state after stress. The approaching behaviors of rats were detected by the test of Agmo, which contained two parameters: partner preference score and time spent with female/male. After behavior tests, all rats were deeply anesthetized and anatomized, the testicular was obtained. After Paraffin embedding and HE dyeing, using light microscope, the following parameters were measured: diameter of seminiferous tubule, Thickness of seminiferous epithelium, number of Seminiferous epithelium cells, area of leydig cells, area of sole leydig cell, number of leydig cells. On the other hand, we used transmission electron microscope to identify the cellular structure and organelles form of leydig cells, sertoli cells and Spermatogenic cells between control group and model group,to find the effect of chronic stress on the testicular.Results:(1) Effects of chronic stress on emotional state: Under progress of chronic stress, the body weight was significantly reduced from the day of 14, and retained to the day of 35. Compared with the control group, model group’s sugar intake scores was significantly reduced (p<0.01). In open-field experiments, the moving distance and the standing frequency of model group were significantly reduced (p<0.05, p<0.01), the residence time in central area, the frequency of acrossing central area, dejecta grains had increased (p<0.05, p<0.01, p<0.05).(2) Effects of chronic stress on approaching behaviors: The male rats of model group showed the same partner preference score and time spent with female/male, when they facing the diestrus female rat and estrus female rat. Compared with the control group, when the female rat was on her estrus phase, the partner preference score and the time spent with female of model group had reduced(p<0.001, p<0.01), the time spent with male had increased( p<0.01).(3) Effects of chronic stress on testicular, which detected by light microscope: Compared with the control group, the following parameters of model group were all reduced: diameter of seminiferous tubule(p<0.01), Thickness of seminiferous epithelium(p<0.01), number of Seminiferous epithelium cells(p<0.001), area of leydig cells(p<0.01), area of sole leydig cell(p<0.01), number of leydig cells(p<0.01).(4) Effects of chronic stress on testicular, which detected by transmission electron microscope: Compared with the control group, in Spermatogonia of model group , large vacuoles were appeared between cytoplasm and nucleus; in Spermatocytes of model group, it showed distended Endoplasmic reticulum, enlarged mitochondria, and large vacuoles; Spermatids in of model group, it also showed distended Endoplasmic reticulum nucleus and large vacuoles.The sperm’s fibrous sheaths fractured and distended. The model group’s leydig cells appeared distended Endoplasmic reticulum, the nuclear membrane was shrunken and formed a deeply convoluted profile, the nuclear chromatin was aggregated.Conclusion: Chronic stress damaged the ablity of emotion regulation of rats, made the rats depression. At the same time, chronic stress could also inhibited the sex behavior of rats. And the reproductive functions could also been injuried by chronic stress.The inhibited of sex behavior was related to the destruction of leydig cells.
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