Effects Of Stress On The Behavior And Learning Of The Rat Offsprings

People will confront more stress cases with society's increasing competitive pressure, the physical and psychology diseases caused by stress have been increaseingly paid attention on by many persons. Pregnancy is special for women, during this time ,women will also meet some stress cases, the question that whether stress can affect the offsprings has been a very popular topic between the scientists and scholars. In order to understand the effects of prenatal stress on the offsprngs' behavior and learning, in our experiment, stress group was inflicted each day during the pregnancy,and then we detected the offsprings' behavior and learning, and then we detected the expression of cAMP-responsive element binding protein( CREB) and brain derived neurotrophic factor ( BDNF) in the offsprings' hippocampus.Material and method1 ObjectPure breed Wistar rats were bought from Zhengzhou University laboratory animals center. There were 32 female rats and 8 male rats.2 Methods2.1 Modeling: The female and male rats were put together at 22:00 and then the female rats were given vaginal smear examination at 8:00 next day. The female rats were regarded as pregnancy if there were spermatozoa in the vagina smear. The pregnancy rats were randomly divided into control group and stress group. The rats from the control group were reared normal and the stress group was given restraint stress. When the female rats were pregnancy 19 days, we took suction 1ml blood from the tails of the female rats, then we used enzyme linked immunosorbent assay (ELISA) to analyze glucocorticoids. At last we used one-month old young rats totake the experiment.2.2 Behavior test: We used the Open-Field facility to detect the rats'behavior. We regarded the number of the gallery grids that the rats steped over as the gallery level activity scores; We regarded the number of the rats' hindlimb standing as the vertical activity scores. Then we wrote down the gallery level activity scores and the vertical activity scores.2.3 learning and memory test: We used Y-electric maze to detect the young rats' learning and memory. Then we wrote down the third day' scores.2.4 Collecting the sample: After the experiment of Y-electric maze, every one-month old rat was anesthetized,after that the brain tissue was imbeded in paraffin within 24 hours, slicing, making HE staining and immunohistochemistry staining.2.5 Determination of the expression of CREB and BDNF: we used computer image analysis system to select positive area and measuring the gray scale on immunohistochemistry staining slice, then we caculated the mean gray scale(OD). We used the OD to analyse the expression of CREB and BDNF.3 Statistics analysisWe used SPSS15.0 statistical package to analyze the data,all the results weredemonstrated by mean±standard((x|-)±s )deviation,using Independent-Sample T test andanalysis of variance to compare the mean of each group and we regardedα=0.05 as the standard result.Result1 the glucocorticoids resultsThe glucocorticoids comtemt of the female rats in the stress group (41.95±10.47) was obviously more than the control group (20.58±9.39) t=16.836, P=0.027. The result indicated that prenatal stress could improve the glucocorticoids comtemt. 2 The open-field resultsThe gallery level activity scores and the vertical activity scores of the stress group were both higher than the control group (gallery level activity scores F=6.578, P=0.003; vertical activity scores F=7.254, P=0.002) ;There was no difference between female rats and male rats (P>0.05) .3 The Y-electric maze resultThe Y-electric maze scores of the stress group were lower than the control group (F=7.921, P=0.002) ; The female and male rats had no difference (P>0.05) .4 HE stainingNo matter female or male rats, the align of the dentate gyrus granular cells in hippocampus of the stress group were more loosening and tangle than the control group.There was no difference in hippocampus volume and shape between stress group and control group.5 Immunohistochemistry staining5.1 CREB expressed mainly in dentate gyrus granular cells of hippocampus and mainly expressed in nucleolus. It also expressed in CA1 and CA2 .The colour was buffy.The expression in female stress group (87.77±6.34) was significant lower than the control group (92.51±6.53) P <0.05; The expression in male stress group(86.73±7.25) was also lower than the male control group (93.33±6.43) P <0.05. There was no difference between female and male rats (P> 0.05) .5.2 BDNF expressed mainly in CA1 area and dentate gyrus granular cells of hippocampus and mainly expressed in cytolymph .The expression in female stress group( 86.96±7. 32 )was significant lower than the control group( 94.85±6.96 )P<0.05; The expression in male stress group (87.32±7.00) was lower than the control group(95.32±7.01) , P <0.05. There was no difference between female and male rats (P >0.05) .Conclusion1. Prenatal stress may induce the low expression of CREB and BDNF in the offsprings 'hippocampus tissues of the rats. 2. Prenatal stress may induce the rats offsprings to appearance emotion disorder such as hyperactivity and excitation.3. Prenatal restraint stress may descent the rats offsprings' learning and memery.4. The effect of prenatal restraint stress on the rats offsprings had no sex differences.