Stereological study on the relationship between the differences in stress susceptibility and dendritic spines changes in the CA3 and DG of hippocampal formation in depression

Abstract:

Objective：To investigate the differences of dendritic spines in the CA3 and dentate gyrus（ＤＧ） of the hippocampal forma－tion in normal control group，chronic unpredictable stress（CUS） susceptibility group and CUS resistance group in order to further un－derstand the structural bases of the depression-like behaviors. Methods：Four-five weeks old male SD rats were randomly divided into normal control group and model group. The model group rats were treated with chronic unpredictable stress for 4 weeks. Then，the model group rats were randomly divided into the CUS resis－tance group and the CUS susceptibility group according to the results of sucrose preference test. The numbers of dendritic spines in the CA3 and DG of the hippocampal formation of normal control（n=5），CUS susceptibility group（n=5） and CUS resistance group（n=5） were quantitatively estimated using the stereological methods and immunohistochemical methods. Results：The sucrose preference in the CUS susceptibility group rats was significantly decreased when compered with that of the CUS resistance group and normal control group（P=0.000，P=0.000）. The sucrose preference in the CUS resistance group and normal con－trol group was not significantly different（P=0.262）. The total number of the dendritic spines in the CA3 of the CUS susceptibility group rats was significantly lower than that of the normal control group and that of the CUS resistance group（P=0.008，P=0.004）. The total number of the dendritic spines in the DG of the CUS susceptibility group rats was significantly lower than that of the normal control group and that of the CUS resistance group（P=0.001，P=0.001）. The total number of the dendritic spines in the CA3 and DG in the normal control group was not significantly different when compared with that of the CUS resistance group（P=0.656，P=0.950）. Conclusion：The total number of the dendritic spines in the CA3 and DG of the hippocampal formation in the CUS resistance group was not affected by CUS intervention，suggesting that the number of dendritic spines in hippocampus might be one of the key factors for the difference of stress susceptibility in depression. Our study might provide one of the important structural bases for searching the new treatment direction of depression.