Effects Of Exercise On The Oligodendrocytes In The Hippocampus Of The Rat Model Of Depression

PartⅠ The stereological investigation on the changes of the oligodendrocytes in the hippocampus of the rat model of depressionObjective: The depressed rats induced by chronic unpredictable stress were used in the current study. Then, the changes of the CNPase+ oligodendrocytes in the subregions of the hippocampus were investigated with the unbiased stereological methods in order to provide the scientific evidences for further understanding the structural bases of the pathogenesis of the depression and for searching the new therapeutic target of the depression.Methods: 4~8 weeks old Male Sprague-Dawley(SD) rats were randomly divided into the control group and CUS group. In order to establish the rat model of depression, the rats were treated with the combination of CUS and separation for four weeks. The sucrose preference was used to screen the depressed rats induced by chronic unpredictable stress(CUS) at the end of 4th week. Then, 10 rats in CUS group and 10 rats in control group were randomly selected to the research for the first part. Meanwhile, the effects of chronic unpredictable stress on the behaviors were investigated by means of open field test and forced swimming test. For the quantitative part, six rats in each group were randomly selected. One hemisphere of the brain was randomly selected for each rat and serial sections of the hemisphere with the thickness of 60μm were cut on a freezing microtome. The hippocampal tissues were sampled in a systematic, random fashion, with the first one being randomly sampled in the first 6 sections. The combinations of the immunohistochemical methods and the modern stereological methods were used to precisely quantify the total number of the CNPase+ of oligodendrocytes in each subregion of hippocampus.Result: The results indicated that CUS group induced a decrease in body weight, the sucrose preference, the total score in open field test when compared to control group(p<0.05, p<0.05, p<0.05). Also, the immobility time in CUS group was longer than that in control group(p<0.05).The stereological results showed that there was no significant difference in the CNPase positive cells in the CA1 field of the hippocampus between CUS group and control group(p>0.05). In contrast, the CNPase positive cells in CUS group were significantly decreased in CA3 and DG areas when compared to control group(p<0.05, p<0.05).Conclusions: We found that there was a significant decrease in the CNPase-positive cells in the CA3 and DG of rat hippocampus which indicated that the oligodendrocytes might be involved in the pathogenesis of the depression. The present results might not only provide important theoretical evidence for the pathogenesis of the depression, but also open a new direction for exploring the possible new therapeutic targets in depression. PartⅡ The effects of exercise on the oligodendrocyte in the hippocampus of depression model ratsObjective: Our study was to investigate the effects of exercise on CNPase+ oligodendrocytes in the hippocampus of the rats model induced by Chronic Unpredictable Stress(CUS) with the immunohistochemical technique and the unbiased stereological methods in order to provide important scientific basis for exploring the structural targets that ruuning exercise alleviated the depression through it.Methods: After 4 weeks of CUS, the remainded CUS group were randomly divided into the CUS control group(10 rats) and the CUS exercise group(10 rats). Then, a 4-week treadmill running trial was performed to CUS exercise group. Meanwhile, the effects of exercise on the behaviors of the rats induced by chronic unpredictable stress were investigated by means of sucrose preference, open field test and forced swimming test at the end of 8th week. The combination of the immunohistochemical methods and the modern stereological methods were used to precisely quantify the total number of CNPase+ oligodendrocytes in each subregion of hippocampus.Result: The results indicated that CUS control group and CUS exercise group were still lower than control group in body weight(p<0.05). However, the sucrose preference of CUS control group was significantly lower than control group and CUS exercise group(p<0.05, p<0.05). The total score in open field test of CUS control group were significantly lower than that in control group, but there was no significantly difference between the CUS exercise group and control group(p<0.05, p>0.05). And the immobility time in CUS control group was still longer than that in control group(p<0.05). Also there was no significantly difference between the CUS exercise group and control group(p>0.05). The results showed that there was no significant difference in the CNPase positive cells in the CA1 field of the hippocampus among the three groups(p>0.05). In contrast, the CNPase positive cells in CA3 and DG area of CUS control group were significantly decreased when compared to CUS exercise group(p<0.05), whereas no significant differences were found in these parameters between the CUS control group and the control group(p>0.05).Conclusions: 1.The present results further confirmed that exercise could improve the symptoms of depression rats. 2.Exercise might protect the oligodendrocytes in the hippocampus of the depression rats. The protective effect of running exercise on the oligodendrocytes in the hippocampus of the depressed rats might be one of the important structural bases for the fact that ruinning exercise improved the depression-like symptoms.