| Objective:Alzheimer’s disease is the most common dementia in the elderly.The disease is mainly neurodegenerative disease,which is characterized by many neurons and synaptic apoptosis in the brain.The clinical characteristics are mainly cognitive dysfunction,behavior and personality changes.Progressive irreversible lesions can be observed in Alzheimer’s disease,especially in cortical and hippocampal neurons.In addition,there will be extracellular aggregation of beta amyloid plaque and nerve fiber tangles consisting mainly of Tau protein.Sporadic Alzheimer’s disease is one of the slow progression of neurodegenerative diseases that can be secrecy and progressively deteriorate and eventually lead to delayed dementia symptoms.The disease accounted for 90%of the total incidence of AD and the elderly often occur in 65 years later.Streptozotocin is a natural compound,which produced by Streptococcus,with specific toxicity to mammalian insulin production in the pancreas islet β cells and often used to establish a model of type one diabetes mellitus.Many reports showed that the application of streptozotocin could produce sporadic Alzheimer’s disease pathology typical change.Transgenic APP/PS1 mice express human mutant amyloid precursor protein and transformation into amyloid material,the aggregation of amyloid deposits leads to plaque formation.The animal model is a commonly used in the field of Alzheimer’s disease research.However,whether is there more serious pathological and behavioral changes after giving the external pathogenic factors when the existing of the genetic background pathogenic conditions but which have not yet shown significant changes in behavior and pathology?Or accelerating the progrosss of AD?There’s no report for now.Therefore,the main purpose of this study is to explore whether behavioral abnormalities and Alzheimer’s disease related pathological changes may occur and accelerate the AD progress in mice by using streptozotocin in transgenic APP/PS1 mice of low age(2-month-old)which have not yet shown significant changes in behavior and pathology.Thus,we could offer some evidences for the controlling of the AD process in clinical practice.Methods:The genotypes of transgenic APP/PS1 mice were identified by breeding.The experimental mice were divided into APP/PS1+STZ group/APP/PS1+STZ group,C57 mice group/C57 group.Streptozotocin was injected into the lateral ventricle of the experimental group by the technology of intracerebroventricular injection.After 4 weeks,the behavioral changes of mice were measured by water maze,open field test and novel object recognition experiment at the fifth weeks.After the test of performing behavioral,the mice were killed and their brains were removed and fixed,frozen and sliced,then cryopreservation of floating tablets.To identify the amyloid protein by immunohistochemical staining,thioflavin S staining and congo red staining and observe the morphological changes of hippocampal vertebral body by HE dyeing method.Results:The water maze test result showed that there was no significant difference between groups.In the open field test,compared with the C57 group,there were significant differences in the three groups of APP/PS1+STZ group,APP/PS1 group and C57+STZ group in the average grooming times(P<0.05).There was a significant difference in average standing frequency between C57+STZ group and C57 group(P<0.05).There was a significant difference between the C57+STZ group and the C57 group in the average central area residence time(P<0.05),and there was also a significant difference between the APP/PS1+STZ group and the APP/PS1 group in the average central area residence time(P<0.05).Novel object recognition experiment showed that there was significant statistical difference between the C57+STZ group and the C57 group,the APP/PS1 group and the C57+STZ group on the average time of use in the new area(right area)(P<0.05).In addition,there was a significant difference in the average time between the APP/PS1+STZ group and the C57 group in the new area(right area)(P<0.05).In the old things area(left area)and the new area(right area)in total usage time,there was a significant statistical difference between the APP/PS1 group and the C57+STZ group(P<0.05).Immunohistochemical results showed that the specific brown precipitates were clustered and appeared in the APP/PS1 group.The APP/PS1 group also found specific brown precipitates in the cortical area,but the number was very few,only sporadic distribution.No specific brown precipitates were found in the C57+STZ group and the C57 group.The results of HE staining showed that in the APP/PS1+STZ group,some cells in hippocampal CA1,CA2 and CA3 areas were vacuolated,cytoplasm reduced,and the nucleolus disappeared.Other parts of the cell are deeply dyed,retraction,and have morphologic differences between each other.The cells in these areas have different degrees of damage,and the overall arrangement is loose.In the APP/PS1 group,the cells in in hippocampus region CA1,CA2 and CA3,cells were colored moderately,nucleolus was visible,cell morphology was homogeneous,and arranged orderly and denser.In the C57+STZ group,the cells in in hippocampus region CA1,CA2 and CA3 showed vacuolization and pale coloration,but nucleolus was still visible,and the overall arrangement was neat.In the C57 group,the cells,which in in hippocampus region CA1,CA2 and CA3,coloring is moderate,the nucleolus is visible,the cell shape is homogeneous,the whole arrangement is neat and dense.The results of thioflavin S showed that many specific fluorescent stain spots appeared in the brain slices of APP/PS1+STZ group,which were massive,mainly distributed in the cortex and hippocampus.The specific fluorescent stain spots were also found in the APP/PS1 group,mainly located in the cortical area,but the number and size were smaller than those in the APP/PS1+STZ group.In C57+STZ and C57 groups,there was no specific fluorescent stain spots.The congo red staining result showed that many orange red stain spots appeared in the brain slices of APP/PS1+STZ group,distributed in the cortex and hippocampus.Compared with the APP/PS1+STZ group,APP/PS1 group also found specific stain spots,but the number was significantly less than the APP/PS1+STZ group,and only distributed in the cortical area.In C57+STZ and C57 groups,there was no specific staining spots.Conclusion:By the method of injecting STZ into transgenic APP/PS1 mice’intracerebral(2-month-old),many Alzheimer’s disease’s characteristic Aβ precipitates are induced,and damage the hippocampal cells,and have the symptoms of Neuropsychiatry.According to the experimental results,it is speculated that under the background of hereditary pathogenic factors,it is possible to accelerate the occurrence of Alzheimer’s disease related pathology and behavioral changes by giving exogenous pathogenic factors... |
