The Effect Of Chronic Unpredicted Mild Stress On The Apoptosis Of Astrocytes In The Hippocampus Of Rats

Objectives In order to observe the effect of chronic unpredicted mild stress on the apoptosis of astrocytes in the hippocampus of rats.Methods Ninety healthy adult male Sprague-Dawley rats were stochastically divided into model group and control group(n=45).Rat depression model was prepared using CUMS.11 kinds of stress were applied,including 4 ℃ice-water swimming for 5 min,squirrel cage tilted 45 ° for 24 h,double ear electric shock 5S two times(0.8m A),fasting 24 h,continuous illumination 24 h,42 centigrade hot water swimming 5min,behavioral restrictions for 2h,wet pad for 24 h,clamp for 90 s,water deprivation for 24 h,the cage is shaken for 15 minutes.A stimulus was randomly given every day for 28 days,requiring that the same kind of stimulus be discontinued.The control group was given normal feeding.After the end of stress,behavioral tests were carried out in rats by sugar water preference experiment,open field experiment and Morris water maze test,rats were sacrificed at 1d,7d,and 14 d after modeling respectively.Rats in the control group were sacrificed in the same time as the model group.The expression level of apoptotic protein and anti apoptotic protein in hippocampus of rats was detected by Western blot.The confocal distribution of glial fibrillary acidic protein(GFAP)and Bax,GFAP and Bcl-2,GFAP and Caspase-3 in hippocampus of CUMS rats were observed by laser scanning confocal microscopy.SPSS 17.0 statistical software was used to analyze the data of the experiment,and the difference was statistically significant with P < 0.05.Results Sugar water preference experiment: there was no great difference in pure water consumption between the control group and the model group(P>0.05).Rats in the model group had significantly lower sucrose consumption and sucrose water percentage preference than the control group(P<0.01).Open-field experiment: The total distance of walking,the time of central activity,erection frequency,and number of modification behaviors in the model group were significantly decreased than those in control group(P<0.01).Morris water maze test: The average escape latency of rats in the model group was higher than that in the control group(P<0.01).In the results of Western blotting,according to the strip analysis,compared with the control group,the expression level of Bax and Caspase-3 protein in Rat’s hippocampus at 1d,7d,and 14 d after CUMS was increased(P<0.05),and the most significant increase was in 7d(P < 0.05).The expression of Bcl-2 protein in the hippocampus of rats at 1d,7d,and 14 d after CUMS decreased in comparison with that of the control group(P<0.05).Immunofluorescencedouble-label results: GFAP was green fluorescence with Alexa Fluor 488 excitation,Bax was red fluorescence with Alexa Fluor 594 excitation,and yellow fluorescence was seen after image fusion,indicating that GFAP and Bax can be expressed simultaneously.Compared with the control group,the fluorescence fusion of GFAP and Bax in the hippocampus of the model rats was more extensive.The results of GFAP and Bcl-2 in hippocampus of rats of 7d after CUMS show that: GFAP is Alexa Fluor 488 excited green fluorescence,and Bcl-2 is Alexa Fluor 594 excited red fluorescence,yellow fluorescence can be seen after image fusion,indicating that GFAP and Bcl-2 are expressed simultaneously;The fluorescence fusion of GFAP and Bcl-2 in the hippocampus of the model rats was significantly lower than that in the control group.The results of GFAP and Caspase-3 in hippocampus of rats of 7d after CUMS show that: is Alexa Fluor 488 excited green fluorescence and Caspase-3 is Alexa Fluor 594 excited red fluorescence,yellow fluorescence can be seen after image fusion,explain the simultaneous expression of GFAP and Caspase-3.Compared with the control group,the fluorescence fusion of GFAP and Caspase-3 in the hippocampus of the model rats was more extensive.Conclusions 1 The animal model of depression was successfully established in rats with CUMS.2 After CUMS,there is apoptosis in the hippocampus of rats.3 The expression of apoptosis related protein and astrocyte specific marker protein is co-located,suggesting that the apoptosis of astrocytes is enhanced,which may be one of the reasons that affect the volume of hippocampus in depressive rats.