STUDIES ON REGENERATION OF THE NEURONAL NETWORK IN CEREBROVASCULAR DEMENTIA MODEL

在本研究项目中，我们研究了微球栓塞术(ME)后，海马脑片上M受体(MAChR)信号转导通路的变化。我们的研究结果表明，刺激mAChR不能激活缺血大鼠同侧的MAPK，但不能激活对侧的MAPK。卡巴胆碱刺激mAChR可诱导对侧海马区Gα_(11)&gt；亚单位酪氨酸磷酸化，但不能引起同侧海马区酪氨酸磷酸化。这些结果表明，mAChR诱导的脑缺血大鼠海马区Gα_&lt；Q/11&gt；亚单位酪氨酸磷酸化的失败可能与ERK信号转导的改变有关。我们进一步研究了Me对大鼠海马神经元网络再生的影响。免疫组织化学研究显示，轴突出芽的标志物GAP-43、突触前神经的指示物突触素和神经营养因子脑源性神经营养因子的表达增加，而黏附分子L1的数量减少。这些结果表明，缺血半影区神经元网络再生的部分因素，但不是全部因素，对持续一段时间的脑缺血作出反应。然而，免疫化学分析显示，ME动物同侧海马区GAP-43和L1蛋白的绝对量减少。ME动物海马区缺血半影区L1表达缺乏，提示脑缺血后细胞黏附分子的产生可能在缺血性脑损伤后中枢神经系统神经元网络的再生中发挥作用。

We investigated changes in signal transduction pathways via muscarinic acetylcholine receptor (mAChR) in hippocampal slices after microsphere embolism (ME) in this term of research project. Our findings demonstrated that stimulation of mAChR fails to activate MAP kinase in the ipsilateral, but not in the contralateral hippocampus of ischemic rats. The stimulation of mAChR with carbachol induced tyrosine phosphorylation of the Gα_<q/11> subunit in the contralateral, but not in the ipsilateral hippocampus. These results suggest that failure in mAChR-induced tyrosine phosphorylation of the Gα_<q/11> subunit in the ischemic hippocampus may be involved in alterations of ERK signal transduction.We further examined alterations in factors involved in the regeneration of the neuronal network in the hippocampus of rats with ME.The immunohistochemical study showed increases in GAP-43, a marker of axonal sprouting ; synaptophysin, a inarker of presynaptic nerve ; and BDNF, a neurotrophic factor and a decrease in the amount of L1, an adhesion molecule in some areas of the hippocampal ischemic penumbra of such animals. These results suggest that some, but not all, factors for regeneration of the neuronal network in the ischemic penumbra respond to sustained cerebral ischemia for a certain period. Immunochemical analysis, however, showed decreases in the absolute amounts of GAP-43 and L1 proteins in the ipsilateral hippocampus of the ME animal. The lack of an increase in L1 in the ischemic penumbra of the hippocampus of the ME animal suggests that production of cell adhesion molecules in response to cerebral ischemia may play a role in the regeneration of the neuronal network of the central nervous system after ischemic brain injury.