反复性脑缺血致丘脑神经元损害的动态观察(英文)

Dynamic observation on neuronal damage in thalamus induced by repetitive cerebral ischemia

背景:反复非致死性短暂脑缺血导致神经元累积性损害和血管性痴呆,确切的损害型式和机制至今不甚明了。丘脑是学习记忆的重要结构,同时亦为脑缺血选择性易损区,但目前研究报道较少。目的:探讨反复性脑缺血丘脑神经元的病理损害及其发生机制。设计:随机对照实验研究。单位:解放军成都军区总医院神经内科。对象:实验于1999-03/12在解放军第三军医大学中心动物实验室完成。选择健康雄性Wistar大鼠72只,随机分为假手术组、单次脑缺血组、反复脑缺血组、MK-801治疗组和生理盐水组。方法:采用改良Pulsinelli4-血管闭塞法,分别建立大鼠单次缺血15min和以1h为间隔反复缺血3×5min的全脑缺血动物模型,并再灌注5h、2d、4d。假手术组不灼烧椎动脉,不夹闭颈总动脉。应用45Ca放射自显影及光镜对比观察单次性脑缺血和反复性脑缺血及NMDA受体拮抗剂KM-801治疗后丘脑钙积聚和神经元损害的病理改变。主要观察指标:观察各组大鼠丘脑钙积聚与神经元损害的分布和程度。结果:假手术组丘脑无异常钙积聚和神经元损害。缺血再灌注5h,反复缺血组丘脑轻度异常钙积聚,神经元损害亦相对重于单次缺血组(0.98±0.19,0.60±0.14,P>0.05)。缺血再灌注2d,丘脑明显异常钙积聚与神经元损害,钙积聚程度与神经元损害记分反复缺血组显著重于单次缺血组(1.62±0.31,0.88±0.21,P<0.01)。缺血再灌注4d,丘脑异常钙积聚和缺血性损害进一步增强,以反复缺血组最为显著(1.80±0.21,1.02±0.23,P<0.01),尤其丘脑腹侧呈现显著异常钙积聚与累积性损害。MK-801明显减轻丘脑异常钙积聚与神经元损害,与生理盐水组比较,具有显著的神经元保护作用(1.80±0.15,0.20±0.12,P<0.01)。结论:反复非致死短暂脑缺血导致丘脑腹侧神经元显著累积性损害,兴奋性氨基酸及Ca2+可能起重要作用。

BACKGROUND： Repetitive brief and non-lethal cerebral ischemia can produce cumulative neuronal damage and vascular dementia; however, precisely injured patterns and mechanisms are still unclear. Thalamus is an important structure of learning and memory; meanwhile, it is also one of the selectively vulnerable regions of cerebral ischemia. However, there are a few reports about neuronal damage induced by repetitive cerebral ischemia. OBJECTIVE： To investigate the pathological damage and mechanism of neurons induced by repetitive cerebral ischemia in thalamus. DESIGN： Randomized controlled experimental study. SETTING： Department of Neurology, General Hospital of Chengdu Militar）, Area Command of Chinese PLA. MATERIALS： The experiment was carried out at the Animal Central Laboratory of the Third Military Medical University of Chinese PLA from March to December 1999. A total of 72 healthy male Wistar rats were randomly divided into sham operation group, single cerebral ischemic group, repetitive cerebral ischemic group, MK-801 treatment group and saline group. METHODS： Transient global cerebral ischemia models of rats were established with modified Pulsinelli-4 vessel occluing method for single 15- minute ischemia and repetitive three 5-minute ischemia at hourly intervals, followed by 5 hours, 2 days and 4 days of survival. Rats in sham operation group were not treated with burning vertebral artery and clipping common carotid artery. ^45Ca autoradiography and light microscopy were used to determine the calcium accumulation and neuronal pathological changes of thalamus following repetitive cerebral ischemia as compared with single cerebral ischemia. The effects of MK-801, a N-methyl-D-aspartate （NMDA） receptor antagonist, were also examined. MAIN OUTCOME MEASURES： Distribution and degree of calcium accumulation and neuronal damage in the thalamus of rats in each group. RESULTS： Sham-operated rats revealed no abnormal calcium accumulation and neuronal damage in the thalamus. At 5 hours following ischemia, slightly abnormal calcium accumulation was found in the partial thalamus of the repeated ischemic group, and the neuronal damage was also relatively severer than that in the single ischemic group （0.98±0.19, 0.60±0.14, P 〉 0.05）. At 2 days after ischemia, obviously abnormal calcium accumula tion and neuronal damage were shown in thalamus, and the degree of cal- cium accumulation and score of neuronal damage in repeated ischemic group were significantly severer than that in single ischemic group （1.62±0.31, 0.88±0.21, P 〈 0.01）. At 4 days, the thalamus calcium accumulation and neuronal damage were further increased, and also that in repeated ischemic group was significantly severer than that in single ischemic group （1.80±0.21, 1.02±0.23, P 〈 0.01）, especially marked calcium accumulation and cumulative damage were shown in the ventral thalamus. MK-801 significantly relieved the abnormal calcium accumulation and neuronal damage in the thalamus in repeated ischemic group, showing significant protection of thalamus neurons as compared with that in saline-treated group （0.20±0.12, 1.80±0.15, P 〈 0.01）. CONCLUSION： Repetitive non-lethal cerebral ischemia results in an intense cumulative damage in the ventral thalamus, and the excitatory amino acid and Ca^2＋ may play a major role in it.