Positron Emission Tomography Of Two Types Of Depressive Animal Models

This study planted to establish 2 different types of depressive animal models ------- chronic unpredictable mild stress model, post spinal cord injury depressive model. Examing the charactors of the brain function, identifing the specific depression-related encephalic regions of each model by positron emission tomography(PET). And the animal models can also be used in the research of pathology and pharmacology.This paper is to report part of the improvement of this study .The reasons why Post SCI(spinal cord injury )depressive animal model has not been reported by now may be the demanding surgery skills , the complex post operation care , the extradinery high death rate, and the defficulties in depressive symptom assess which have been proved by our works. However, in the study of the machanism of depressive disorder, SCI can not be neglected as one of the most important pathogenic factors. It is reported that there are 95-97% post SCI patients will suffer from depresion within 1 year, and 20% of which will be the heavy type who will be faced with 5 times higher suicide risk rate. Almost every SCI patient suffered from severe psychologic disorders such as anxiety , depression, agitation , inferiority, even some symptoms of schizophrenia. The spinal cord injury which is inevitably followed by depressive disorder have affacted the patients so seriously that made itself one of the most pressing issues of medical prectice. The high degree of correlation between SCI and depression remand us that the establishment of the post SCI depressive animal model is not only possible but also indispensable. After repeated experiments, we finally succesded in getting the post SCI depressive rats model by cross-section the spinal cord between the 9th and the 10th choracic vertebra together with post operation isolation. This model showed good face validity in a series of classic behavioral tests such as the sucrose preference test,the open-field test,and the force swimming test. And assess of the other two validities will be studied in our following work. With PET screening,we get images seemed similar with the CUMS model's.CUMS( chronic unpredictable mild stress) depressive rat model is one of the most popular depression animal models now. It is enthusiastically welcomed by researchers for its facility, prosperity and good validity. We successfully duplicated this model and get 3 groups of rats --------normal rats of control marked as C, depressive rats after treatment marked as CUMS, rats without depressive symptoms after treatment marked as ND. After the screening of PET , we find in the regions of prefrontal cortex, hippocampus, corpus striatum, insular lobe, thalamus, hypothalamus, cingular gyrus, corpus callosum and interal capsule depressive rats has heightened glucose metabolism rate than those who are not depressive , while in the region of temporal and occipital lobe, cerebellum, some nucleus of hippocampus, thalamus and hypothalamus glucose metabolism rate are reduced.By examining the images of these two models ,we get the impression that with the respect of depressive rats, the heightened glucose metabolism brain regions are scattered in the wide range of front part of the head, while the reduced region are concentrate on the back part, roughly symmetrical between the right and left part of two cerebral hemisphere.These results are agree with what have been found about the brain function charecters of depression petients by the examinations of fMRI and PET. It tells us that the depression affact not only some specific brain regions , but also change the nomal interaction of defferent parts of the brian. And our results add new prooives to Drevets'depressive loop circuit.That is what we have gotten from our experiment by now. There are still many problems remain unsolved with the respect of animal models. We should examine the other two validities-------constructive and predictive validity of the post SCI depression rat model to make sure that it is appropriate. For CUMS model, we need to repeat its'PET screening results.With the instruction of PET image, we get biological samples of the two rat model. They are serum, brain tissue of cerebral cortex, hippocampus, corpus striatum, piriform and amygdaloid nucleus, brain stem, septum area, thalamus, hypothalamus, cerebellum and olfactory bulb, et al. More proteomic researches will be launched on these samples in the near future.