Contrasting Research Of Animal Models In Vascular Dementia Induced By Spontaneously Hypertensive Rats And Non-Hypertensive Rats

Background: According to the international classification system DSM-â…£and ICD-10, dementia is defined as an acquired decline of mental functions, inrelation to the patients previous level of function. To meet the criteria of theinternational classification system DSM-â…£and ICD-10, more than onecognitive function has to be impaired and memory disturbances have to bepresent. Apart from memory, mental impairment may extend to abstractthinking, judgment, higher cortical functions, visuospatial skills, motorperformance, emotional functionals and personality change. With theconditions of medical treatment and public health developing, the meansurvival age, in worldwide rose from 36.4 years in 1950 to 64.7 years in 1990.Then percentage of population over 65 years do also increase with the risingsurvival age.So it is necessary to study the diseases and disorders the "old men"suffer from. Insufficiency of the brain, which if it is severe, is termed dementia,is indeed a common disorder. For dementia of all types, the incidence figure peryear in people aged 65 and older is closed to 1%,and the prevalence ofdementia is considered to be 5-10% in people over age 65, 0.8% between ages65 and 70,and almost 50% over age 95.Vascular dementia(VD) as one type of dementia is more popular indeveloping countries, such as China, than in developed countries. However theexact reason resulting vascular dementia is not very clear. A lot of researcherssuggest that the arterial hypertension and chronic hypoperfusion of some cerebralregions (such as cardiac and carotid emboli) probably be the main reasons forvascular dementia. Where are the "pointed"locations to be answered to theVD?Some researches show multiple small thromboembolic strokes or strokesin strategic locations such as frontal lobe, temporal lobes , hippocampi, or thethalami may cause intellectual impairment and frequently occur without classicalstroke-like symptoms. Methods: We adopted the permanent occlusion of bilateral carotid arteries inmale Wistar rats and Spontaneously Hypertensive Rat (SHR) to produce thechronic forebrain ischemia and arterial hypertension which were similar to thehuman chronic cerebral ischemia and hypertensive disease . We estimated theperformance of the rats in the Morris water maze tests to reflect the animal'smemory function. By HE stain ,the morphology change of neuron cell in thefrontal lobe, temporal lobes, hippocampi, or thalami and the arteries in cortexand subcortex would be observed; by LFB stain ,the change of white matteraround the cerebral ventricle would be observed. The neuro-pathology changeswere inspected by light microscopic examination. Through the imaging andstatistics analysis, we investigate the probable mechanism. Results: 1.Behavioral changes. Before the occlusion of bilateral carotidarteries, the rats had been trained to find the platform under the milk water in theMorris water maze in three minutes. we considered the incubation period ofelude as the reflect of the rat's ability in space memory. From the result, wecould conclude that the rat interfered in with the occlusion of bilateral carotidarteries and hypertension was more foolish as compared with the sham operatedgroup and blank group(p<0.05),and the incubation period of elude in theoperation group was prolonger than the hypertension one(p<0.05).However therewas no difference in the sham operated group and blank group(p>0.05). Thoughwe could conclude from the results in Morris water maze tests that chronichypoperfusion and hypertension could result in cognitive impair, andhypoperfusion was a more severity factor than hypertension. 2. Pathological changes. Through the microscope, the degeneration anddetachment of neuron could be observed, so did the necrosis of the neurons andwhite matter around the cerebral ventricle and accrementition neuroglial cells.In the frontal lobe, hippocampus, or the thalamus, there are lots of thedegeneration and detachment of neurons in the ischemia group andhypertension group, which is more severe in the ischemia group than inhypertension one (p<0.05). But both of them are more obvious than the shamoperated group and blank group (p<0.05), in which there are no differences(p>0.05).In the temporal lobes, however, the degrees of the degeneration anddetachment are close to each other in the ischemia group and hypertensionone(p>0.05).So does in the white matter around the cerebral ventricle just likein the frontal lobe, hippocampus, and the thalamus. So we can draw thisconclusion, more demolishes were given by hypoperfusion to neurons andwhite matter than by hypertension. Hyalinization of arteriole could be seen in the regions of the cortex andsubcortex in pathological section. Through imaging analysis, we can read thestenosis in the inner diameter of artery. This phenomenon is more manifested inthe hypertension group than the ischemia group, sham operated group, andblank group(p<0.05). 3.The associativity. After being dealed with the statistics method, the results...