多巴胺耗竭对纹状体神经元在缺血再灌注损伤中的保护作用

PROTECTIVE EFFECT OF DOPAMINE DEPLETION AGAINST STRIATAL NEURONS INJURY DURING CEREBRAL ISCHEMIA AND REPERFUSION

为探讨全脑缺血再灌注损伤过程中多巴胺对纹状体内各类神经元的影响 ,本实验用 6 -OHDA损毁大鼠一侧黑质多巴胺能神经元以耗竭该侧纹状体内的多巴胺 ,再进行 4血管结扎造成全脑缺血模型 ,3 0 min后分别复灌 6、12、2 4h,行连续冰冻切片 ,以焦油紫染色进行形态学分析 ,用 calbindin-D2 8k及 parvalbum in两种钙结合蛋白抗体进行免疫组化反应。结果显示 :(1)焦油紫染色 :缺血 3 0 min复灌 6 h即可见多巴胺未耗竭侧纹状体内神经元损伤比耗竭侧者明显加重 ,复灌 12及 2 4h组双侧差别更为显著 ;图像分析测定单位面积内焦油紫染色细胞面积总和 ,各实验组两侧间均有显著性或极显著性差异 (P<0 .0 5 ,P<0 .0 1) ;(2 ) calbindin-D2 8k免疫组织化学染色 :各组内多巴胺未耗竭侧纹状体 calbindin-D2 8k阳性反应明显比耗竭侧减弱 ,阳性神经元数量减少、染色变浅 ,图象分析显示其光密度明显低于耗竭侧 ;(3 ) parvalbumin免疫组化反应 :同时间组双侧纹状体 parval-bumin阳性神经元的形态和数量无明显差别 (P>0 .0 5 ) ,但随复灌时间的延长 ,双侧阳性细胞数均有降低。以上结果提示 :脑缺血时大量释放的 DA是纹状体神经元缺血性损伤的重要因素之一 ;纹状体内的 calbindin-D2 8k投射神经元对脑缺血及 DA含量的变化敏感 ,?

To explore the effect of dopamine (DA) on striatal neurons during cerebral ischemia and reperfusion, a rat complex model was performed with 6 hydroxydopamine(6 OHDA)lesioned substantia nigra (SN) to deplete DA plus four vessels occulusion for forebrain ischemia. After 30 min of ischemia following 6 h, 12 h and 24 h of reperfusion, the vulnerability of different types of striatal neurons to ischemia was observed by means of cresyl violet stain and calbindin D28k and parvalbumin(two calcium binding proteins) immunohistochemistry. The results were as follows: (1) In cresyl violet sections, the ischemic neuronal damage in the denervated striatum was slight than that in the intact striatum at 30 min ischemia following 6 h of reperfusion. This difference of vulnerablity to ischemia between lesioned and intact sides was more obvious at 12 h and 24 h of reperfusion. The areas of cresyl violet steined cells between the denervated and intact striatum were significant difference in every experimental group(P<0.05, P<0.01). (2) With 30 min ischemia following 6 h, 12 h and 24 h of reperfusion, the intensity of calbindin D28k immunoreactivity(IR) was obviously weaker in intact striatum than lesioned striatum. The number of calbindin IR neurons decreased in intact side. Quantitative image analysis demonstrated that the average optical density of calbindin immunoreactivity in the intact stratum was lower than that in the denervated striatum (P<0.05, P<0.01).(3) No significant differences in the number and shape of parvalbumin IR neurons were found between intact striatum and lesioned striatum(P<0.05), but the number of positive cells was decreased in both striatum following the prolonged time of reperfusion. These results suggest that the excessive release of dopamine during cerebral ischemia and reperfusion is involved in the severe striatal neuronal damage. Striatal calbindin projection neurons rather than parvalbumin interneurons are vulnerable to ischemia and variation of DA concentration. DA depletion may effectively protect this type of striatal projection neurons against ischemia injury. (Figure 4 on plate 20)