Objective To explore the relationship between the effects of mild hypothermia on cerebral ischemic / reperfusion injury and expressions of Bax in hippocampal CA 1 area after forebrain ischemia at the different spots in gerbils and to discuss the possible mechanism of mild hypothemia for brain protection . Methods Forebrain ischemic model in -duced by bilateral common carotid artery obstruction was adopted . The gerbils were randomly divided into 4 groups : sham group ( SH) : sham operated group having the same surgical procedures without bilateral carotid arteries occlusion ; normo-thermic ischemic reperfusion (IR) group: having a 5 min ischemia; hypothermia sham (HSH) group: having the same operation as SH and cooling body temperatures at 33℃ ±0.5℃ for 4 h; hypothermic ischemic reperfusion (HIR) group: having a 5 min ischemia and immediately after reperfusion cooling body temperatures at 33 ℃ ±0. 5℃ for 4 h. At different time spots after ischemia , with the animals designated as subgroups 2h,4h, ld,3d,5d(n=6 in each). The animals' behavior was observed by open field method. The apoptotic neurons were detected in CA 1 area by TUNEL method. The survival neurons of hippocampal CA 1 regions were accounted on H - E staining slides. The expression of Bax in hippocampal CA1 area was detected by SP immunocytochemical technique . Results The behavioral marks and the number of apoptotic neuons in hippocampal CA 1 region were much less in HIR group than in IR group . The number of survival neurons in hippocampal CA 1 region in HIR group was more than that in IR group . The expression of Bax was reduced in the CA1 area in HIR group than in IR group at early reperfusion (2 h, 4 h, 1d). Conclusions Hypothermia can significantly protect neurons against cerebral ischemia , and its protective mechanism involves reducing Bax activation at early reperfusion.%目的 研究亚低温(33℃,4 h)减轻沙土鼠脑缺血/再灌注损伤与海马 CA1 区Bax表达变化的关系,探讨亚低温脑保护的可能机制.方法 采用沙土鼠双侧颈总动脉阻断5 min前脑缺血/再灌注损伤模型,随机分为假手术组(SH)、常温再灌注组(IR)、低温假手术组(HSH)、低温再灌注组(HIR),每组根据再灌注的不同时间点(2 h、4 h、1 d、3 d、5 d)又分为5个对应的亚组(n=6).在预定时间点行开阔法迷宫检查,TUNEL法检测海马CA1区的凋亡细胞,苏木精-伊红染色检测海马存活细胞,免疫组化检测Bax在海马CA1区的动态变化.结果 4 h亚低温可显著减少缺血沙土鼠1 d、3 d、5 d的探索活动及CA1区的凋亡细胞,增加存活细胞,抑制脑缺血后海马CA1区Bax的早期表达(2 h、4 h、1 d ).结论 4 h亚低温对沙土鼠5 min前脑缺血有确切的保护作用,抑制海马CA1区缺血/再灌注早期Bax的表达可能是其减少海马细胞凋亡、产生脑保护作用的机制之一.
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