The Effects Of Methyl-vitaminB₁₂ On Leaning And Memory Following Repeated Forebrain Ischemia-reperfusion In Rats

Vascular dementia is one of the most common dementias in the eldly. Leukoaraiosis is one of the major reasons of vascular dementia, and its major pathological change is local or general myelinolysis in the white matter. The pathological lesions of myelins and oligodendrocytes can be seen under the electron microscope. Demyelination was assessed by using Luxol Fast Blue staining . Therefore , by observing the pathological changes of myelins and oligodendrocytes and the changes of learning and memory ability in the model rats of simulating vascular dementia ,we can investigate the effects of different medicines on leukoaraiosis and vascular dementia. we can conclude that some medicine can be used to treat vascular dementia by treating leukoaraiosis, which opens a new pathway for clinical therapy of vascular dementia.We adopted the repeated occlusion of bilateral common carotid arteries in Wister rats to produce the repeated forebrain ischemia-reperfusion lesions, which produced the models of simulating vascular dementia . Then we treated them with methyl-vitaminB12. We estimate the performance of the rats in the Morris water maze and observed the pathological changes of myelins and/or oligodendrocytes by using election microscope and LFB staining to explore the effects of methyl-vitaminB12 on vascular dementia , whose major reason was leukoaraiosis.45 male Wister rats were divided into 3 groups at random: sham-operation group, ischemia-reperfusion group and treated group. Each group was divided into 1-week group, 2-week group and 4-week group according to its different operation time. Treated rats were given methyl-vitaminB12 every day after operation .Results from the Morris water maze showed that the repeated forebrain ischemia-reperfusion injure leaded to learning and memory impairment of the rats. The rats in the ischemia-reperfusion groups spent longer time than those in sham-operation groups .It appeared that the models of simulating vascular dementia were produced by the repeated occlusion of bilateral common carotid arteries in Wister rats. The learning and memory ability of the treated rats were better than that of the ischemia-reperfusion rats .The former spent shorter time than the latter. It showed that methyl-vitamin B12 were effective to vascular dementia.Results from electron microscope showed that the pathological changes of myelins and oligodendrocytes of the treated rats in the subcortial white matter were apparently lighter than those of the ischemia-reperfusion rats at 4-week after operation. Myelinated neurofibers were transformed from cloudiness of myelinsheats and cavitation of axons and neuropils to the better state of them. Oligodendrocytes with injured plasma membrance ,irregular nuclear, bullosis ground substance and bulging endoplasmic reticulum were changed to those with oval nuclear and better organelles. The LFB myelin staining area of the white matter was widened in the treated group compared with the ischemia-reperfusion group at the same operation point. It appeared that methy-vitaminB12 were effective to leukoaraiosis, whose major pathological change was myelinolysis. Methyl-vitaminB12 are water-soluble vitaminB ,which attend many methylation reactions in the neurous systems. The methyiation reactions are necessary in the formation of ribonucleic acid and myelin protein. The mechanism for methyl-vitaminB12 to therapy myelinolysis is incompletely clear up to now. A lot of researchers suggested that LPA played a role in the myelin repairing .It showed that methyl-vitaminB12 was effective to leukoaraiosis and improved the learning and memory ability of the rats in the experiment. Therefore we concluded that methyl-vitaminB12 were effective to vascular dementia, whose major cause was leukoaraiosis. The effects...