STUDIES ON REGENERATION OF THE NEURONAL NETWORK IN CEREBROVASCULAR DEMENTIA MODEL

本课题研究了微球栓塞（microsphere embolism， ME）后海马切片中毒蕈碱乙酰胆碱受体（muscarinic acetylcholine receptor, 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海马的MAP激酶，而不能激活对侧海马的MAP激酶。恰丁醇刺激mAChR可诱导对侧海马Gα_<q/11>亚基酪氨酸磷酸化，而同侧海马则无。上述结果提示，缺血海马组织中Gα_<q/11>亚基酪氨酸磷酸化失败可能参与了ERK信号转导的改变。我们进一步研究了与ME大鼠海马神经元网络再生有关的因素的变化。免疫组化研究显示，轴突发芽标志物GAP-43升高；突触素，突触前神经的标记物；BDNF（一种神经营养因子）和L1（一种粘附分子）在这些动物海马缺血半暗区某些区域的数量减少。这些结果表明，部分（但不是全部）缺血半暗带神经元网络再生因子对持续一段时间的脑缺血有反应。然而，免疫化学分析显示，在ME动物的同侧海马中，GAP-43和L1蛋白的绝对数量减少。ME动物海马缺血半暗区缺乏L1的增加，提示脑缺血反应中细胞粘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.