| Objective (1)To observe the learning and memory ability changes in chronic aluminium-toxicated rats. (2) To study the pathologic alteration in cerebral cortex, hippocampus and mesencephalon of dementia model group.(3)To study the morphologic changes of dopaminergic neurons in VTA and SN in the dementia model group,control group and the old group,and to analyse the result concluded by image analysing system. (4)To approach the relationship between the morphologic/functional alterations of mesencephalic dopaminergic neurons in VTA, SNC and the dysfunctions of cognitive ability in Aluminium-intoxicated rats.Method Grouping 20 three-month-old male Wistar rats into two groups at random,and taking 10 seventeen-month-old male rats as old group.the learning and memory ability of all rats in the three group were evaluated by darkness-avoiding test, the dementia model group were exposed to aluminum chloride in drinking water (1600mg L-1 ,ad libitum) for 90 days afterwards,then,another identical behavioral test was carried out.Following the completion of the behavioral test,all rats were anesthetized,men perfused with 4% paraformaldehyde,the brains were removed immediately after perfusion.Coronal brain sections were made with freezing microtome.Pathologic changes of assiocated brain regions in dementia model rats were observed by nissl's staining method,silver staining method and immunocytochemistry method,TH immuno-reactive positive neurons in VTA and SNC were counted with image analyzing system,and the data were analysed with SPSS 10.0.Result 1.Behavioral test (1)The electra-striking times and latencies have no significant difference between the dementia model group and the control group beforeexposing to AlCl3 (P>0.5).(2)The electra-striking times increased and the latency decreased in dementia model group after treated with AlCl3(P<0.01).(3)The results of darkness-avoiding test were significantly different between the dementia model group and the control group (P <0.01).(4)The learning and memory ability have no significant changes before- and after the experiment in the control group and the aged rats.2. Pathologic changes:Some NFT-like changes can be observed occasionly in the hippocampus of the dementia model rats,but they were not occurred in other brain regions,and the numbers of them were very limited. Furthermore,some swollen neurons can be found in cerebral cortex,hippocampus and even in midbrain regions. 3 Immunocytochemistry study:The TH+ neurons can only be found in mesencephalic level brain sections,and distributed mainly in VTA and SNC.The density of TH+ neurons in VTA was lower than in SNC,most of them were in fusiform shape, some of them were multangular or elliptic cells.The TH+ neurons distribute densly in SNC,and the neuron numbers in SNC were also more than that in VTA.Most of the TH+ neurons in the dorsal part of SNC were in fusiform shape,but more neurons in the ventral part of SNC were multipolar cells.Compared with the control group,the TH+ numbers in VTA and SNC decreased sharply, and some of them swelled, axons and dendrites shortened or dissolved.furthermore,a very small number of TH+ neurons of which nucleus,axons and dendrites vanished can be observed. 4.The image analysing result: The TH+ neuron numbers in VTA and SNC at five level brain sections were significantly different among three groups (P<0.05).The TH+ neuron numbers in VTA and SNC decreased between the dementia model group and the control group (P<0.05),but there were no significant diference when compared the dementia model group with the aged rats. The OD values were affected significantly in dementia model group,they were not only lower than the control group(P<0.01),but also lower than the old group(P<0.05),but there were no significant difference between the control group and the aged rats.Conclusion 1 )The short-term learning and memory ability of rats decreased aftertreated with AlCl4 chronicaly .2)Aluminium have extensive toxic effects on neurons in different brain regions of rat.3) The NFT-like transformations...
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