The Stereological Study On The Relationship Between The Differences In Depression Susceptibility And Dendritic Spines Changes In The Hippocampal Formation

Objective:To investigate the differences of dendritic spines in the CA₁,CA₃ and DG of the hippocampus formation in normal control group,CUS susceptibility group and CUS resistance group in order to gain a deeper understanding of the structural basis of depression and provide a new direction for the treatment of depression.Methods:4 to 5 weeks old male SD rats?n=100?were randomly divided into normal control group?n=30?and model group?n=70?after sugar adaptive training for 1 week.The number of rats in normal control group is 30.They were divided into 6 cages.The number of rats in model group is 70,and the rats in model group was kept alone.14 different types of chronic unpredictable stress were given for 4 weeks.Body weight and sucrose preference were assessed weekly.Then,the model group rats were divided into the CUS resistance group?n=25?and the CUS susceptibility group?n=25?according to the scores of sucrose preference test.5 rats were randomly selected in each group.One side of the brain was randomly selected from each rat.The selected hemispheres were put into 10%,20%,30%sucrose water?PBS configuration?for 3 d⁴ d dehydration.Then the brain hemispheres was frozen by OCT embedding,and continuous frozen sections were made.The temperature was controlled at-21°C and the frozen section thickness was 60?m.According to the principle of systematic random sampling,the hippocampal tissue was sampled with the sampliy fraction of 1/6.On average,16²0 sections were sampled from the hippocampus of each rat.Under low objective lens?×4?,the boundaries of CA₁ region,CA₃ region and DG region were drawn according to the brain atlas of rats.The numbers of dendritic spines in the CA_1,CA₃ and DG of the hippocampus were estimated using the immunohistochemical method and the stereological method.Results:The body weight in the CUS susceptibility group rats[?292.8±17.5?g]and the CUS resistance group rats[?297.8±19.3?g]were significantly lower than that in the normal control group rats[?326.8±23.5?g]?p<0.05,p<0.05?.The body weight in the CUS susceptibility group rats[?292.8±17.5?g]and the CUS resistance group rats[?297.8±19.3?g]were not significantly different?p>0.05?.The sucrose preference in the CUS susceptibility group rats[?73.6±19.1?%]was significantly lower than that in the CUS resistance group[?95.7±2.6?%]and normal control group[?93.0±11.4?%]?p<0.05,p<0.05?.The sucrose preference in the CUS resistance group[?95.7±2.6?%]and normal control group[?93.0±11.4?%]were not significantly different?p>0.05?.The total numbers of the dendritic spines in the CA₁,CA₃ and DG of the hippocampus formation of the CUS susceptibility group rats[?0.645±0.136?×10⁹,?0.423±0.093?×10⁹,?0.646±0.170?×10⁹]were significantly lower than those in the normal control group[?1.502±0.301?×10⁹,?0.844±0.273?×10⁹,?1.470±0.210?×10⁹]and the CUS resistance group[?1.344±0.208?×10⁹,?0.905±0.226?×10⁹,?1.458±0.375?×10⁹]?p<0.01,p<0.05,p<0.05?.The total numbers of the dendritic spines in the CA₁,CA₃ and DG of the hippocampus formation of the normal control group[?1.502±0.301,?×10⁹,?0.844±0.273?×10⁹,?1.470±0.210?×10⁹]and the CUS resistance group[?1.344±0.208?×10⁹,?0.905±0.226?×10⁹,?1.458±0.375?×10⁹]were not significantly different?p>0.05?.Conclusions:1.The total numbers of the dendritic spines in the CA₁,CA₃ and DG of the hippocampus formation in the CUS susceptibility group rats were significantly decreased when compared to those in the normal control group,but those in the CUS resistance group and the normal control group were not significantly different.2.The number of CA₁,CA₃ and DG dendritic spines in the hippocampus of CUS resistance group was not affected by CUS intervention.The results suggest that the number of dendritic spines in the hippocampus may be one of the important structures in the pathogenesis of depression.