Mr Imaging Of Dementia Rats Induced By 2-vessel Occlusion And Copper Exposure

Objective 1.To study the characteristic behavioral and pathological findings of Alzheimer's disease induced by 2-vessel occlusion and copper exposure.2. To observed MR findings of brain of the Alzheimer's disease model rats with clinical 1.5T MR imager in vivo at different stage, T₂ map was used to assess quantitatively the rat brain in different encephalic regions. To investigate the feasibility that plaques can be detected by MRI in this AD rat model in vivo.Methods Sixty-six SD rats, aged 7⁸weeks, were performed by permanent occlusion of bilateral common carotid arteries(2VO). Six rates dead during operation, the surviving 60 rats were divided into two groups randomly. Group 2VO+Cu²⁺ (n=30) and group 2VO. Group 2VO+Cu²⁺were food with 250ppm copper chloride(CuCl2) in drinking water ( rcontained 5% sucrose ) for 3 months.Control groups included 24 same age rates which were received the same operation but without occlusion of the arteries,The drinking water contained 5% sucrose. At 3th month, 6th month and 9th month after operation, 10 rates selected randomly from each test group and 8 rates from control group were tested by Morris water maze experiment to observe their behavior changes, then performed MR examination using T₁WI,T₂WI,T₂*WI,SWI. T₂ map was used to assess quantitatively T₂ value of the rat brain in different regions. After MR scanning, rates were sacrificed, Whole brains of rates were removed immediately for pathological study (HE staining,thioflavin S staining, immunohistochemistical staining for Aβ,histochemical staining of iron and silver staining ). The SPSS17.0 statistical package (SPSS, Chicago, USA) was used for all calculations.,Mean latent phase and T₂ value of the whole sample at different time-points were evaluated with two-factor measures analysis of variance. Comparison between groups was evaluatated with one-way anova(ANOVA). The results are indicated with mean+standard deviation( x±s) which had a significance level of 0.05.Results A novel complex rat model of dementia were established by permanent occlusion of bilateral common carotid arteries(2VO) and copper exposure for research of AD. After Morris water maze experiment, mean latent phase of VD+Cu²⁺ group and VO group were longer than that of the sham-operated rats(control group)(p<0.05),but there was no significant difference between 2VO+Cu²⁺group and 2VO group(p>0.05). The brains of AD rat model appeared pathological changes of Alzheimer's disease in Group 2VO+CU2+ at the 6th month and the 9th month, group 2VO at the 9th month, which appeared a similar SPs structure, Aβpositive immunoreaction in the cortex and hippocampus .Thioflavin S staining, iron staining and silver staining appeared positive result.some positive appeared in the same brain region. In groups 2VO+Cu²⁺ at the 6th month and the 9th month and groups2VO at 9th month,T₂ value in the cortex and hippocampus of the rat brain descend, there was significant difference compared with control groups. T₂ value had no significant difference in corpus striatum, thalamus and corpus callosum in the rat brain between test group and control group. On MR images with T₁WI,T₂WI,T₂*WI,SWI sequence, some round hypointensity focus can be detected in the cortex and hippocampus of the rat brain in group 2VO+Cu²⁺at the 6th month and the 9th month, group 2VO at 9th month, Preliminary results indicate that T₂*WI acquisition best accurately reflects plaque,T₂WI inferior to T₂*WI,T₁WI have no effect. SWI have best CNR, but it can not remove the effect of blood vessels.Conclusion Dementia Rats induced by 2-vessel occlusion and copper exposure is good model for MR imaging. This rat model appeared the behavioral and pathological changes of Alzheimer's disease. Copper, it can accelerate pathological process of AD. The rat model can be evaluated with MR imaing in vivo.T₂ value descend in the cortex and hippocampus of the rat brain initially, which suggested pathological process of AD.T₂ value may become biological markers of AD. To detect senile plaques with MR imaging in vivo is feasible and deserves further exploration.