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Objective To analyze the neuroimaging changes of tree shrew models of Alzheimer’ s disease.Methods Nineteen healthy adult female tree shrews were randomly divided into control (5 animals) and model group (14 animals). The model of Alzheimer’s disease was induced by intracerebroventricular injection of Aβ1-40 using a stereotaxic devise and proved successfully by visuospatial congnitive task.The in vivo microstructural changes in the brain of tree shrew AD models and control group (0, 1, 2, 3, 4 weeks) were observed on 1.5T MRI (T2WI), and on 7.0T MRI (12 week)(T2WI, DTI). Results Reference memory errors were increased in the model group at 3 or 4 weeks (P<0.05), and so working memory errors (P<0.05) and period of time to perform (P<0.05, P<0.05, P<0.01) from 2 to 4 weeks.Thus the model was proved to be established successfully.T2WI test and DTI test were carried out.Hippocampus atrophy of the model group at 3 and 4 weeks was observed compared with that at 0 or 1 week or 2 weeks on a 1.5T Philips Gyroscan.Compared with the control group, the temporal horn width in the model group was significantly increased (P<0.01) at 12 weeks on a 7.0T Bruker Biospec Scanner.DTI test at 12 weeks showed that ADC of bilateral hippocampus was up-regulated in the model group ( P<0.01 ) .In the color coded orientation view, loss of the corpus callosum fibers was obvious in the model group. Conclusions Intracerebroventricular injection of Aβ1-40 can lead to learing and memory impairment in tree shrews.There are abnomal MRI signal changes in the brain, and the temporal horn width, hypocampal apparent diffusion coefficient ( ADC) value and corpus callosum damage may provide reference value for the diagnosis of Alzheimer’ s disease.
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Objective To investigate the expression levels of BDNF, trkB and ChAT mRNA and proteins in the brain of adult tree shrews ( Tupaia belangeri ) .Methods Quantitative real-time PCR was employed to detect the expression levels of BDNF, trkB and ChAT mRNA in the hippocampus, basal ganglia and frontal cortex of adult tree shrews.The expression levels of BDNF, trkB and ChAT proteins andβ-actin was used as internal standard.Results The expression level of BDNF mRNA was highest in the hippocampus of adult tree shrew, and there were significant differences between that in the hippocampus, and basal ganglia and frontal cortex (P0.05) in the expressions of trkB protein among the hippocampus, basal ganglia and frontal cortex of the adult tree shrews.There were no significant differences in expressions of ChAT mRNA and protein among the hippocampus, basal ganglia and frontal cortex in adult tree shrews ( P>0.05 ) . Conclusions The expression levels of ChAT mRNA were consistent with that of ChAT protein in the hippocampus, basal ganglia and frontal cortex of adult tree shrews, while the expression levels of BDNF and trkB mRNA were not consistent with their proteins, which might indicate that the transcriptional regulation pattern might be more complex.Tree shrew is a valuable animal model in the study of mechanism of BDNF/trkB gene expression.