神经元型一氧化氮合酶在Ⅱ组代谢型谷氨酸受体介导的脑缺血耐受中的作用

目的：探讨神经元型一氧化氮合酶（nNOS）催化产生的一氧化氮（NO）在Ⅱ组代谢型谷氨酸受体（mGluR2／3）介导的脑缺血预处理（CIP）保护机制中的作用。方法：36只永久凝闭椎动脉的SD大鼠随机分为6组（n=6）：sham、CIP、损伤性缺血、CIP4-损伤性缺血、MqPG＋CIP和MTPG＋CIP＋损伤性缺血组。采用硫堇染色和免疫组化观察海马CA1区迟发性神经元死亡（DND）和nNOS表达的变化。结果：与Sham组相比,CIP组海马nNOS表达出现一定程度的上调,而损伤性脑缺血组则出现nNOS表达的明显上调,预先给与CIP可一定程度上防止损伤性脑缺血所致的nNOS表达的过度升高。在MTPG4-CIP组,预先侧脑室注射mGluR2／3阻断剂MTPG,可阻断CIP引起的nNOS表达增加,但对神经元的存活无影响。而在MTPG＋CIP＋损伤性缺血组中,出现大量锥体神经元DND,同时nNOS的表达较MTPG＋CIP组明显增加,该增加为损伤性脑缺血所致,而非MTPG的作用。结论：nNOS催化产生的NO作为mGluR2／3的下游分子参与脑缺血预处理过程中mGluR2／3介导的脑缺血耐受的形成。

The role of NO resulted from neuronal nitric oxide synthase in the metabotropic glutamate receptor2/3 mediated-brain ischemic tolerance

Aim： To explore the role of nitric oxide （NO） resulted from nNOS in the mGluR2/3 mediated-brain ischemic tolerance induced by cere- bral ischemic preconditioning（CIP）, the present study is tmdertaken to observe the influences of α-methyl-（4-tetrazolyl-phenyl） glyeine （MTPG）, an antagonist of mGluR2/3, on the expression of nNOS during the induction of the brain ischemic tolerance based on confirming the blocking effect of MTPG on the induction of the tolerance. Methods： Thirty-six Sprague-Dawley rats, whose vertebral arteries were permanently occluded, were randomly divided into sham, CIP, ischemic insult, CIP ＋ ischemic insult, MTPG ＋ CIP and MTPG ＋ CIP ＋ ischemic insult groups. Thionin staining and immanohistochemistry were used for neuropathological evaluation and assay of nNOS expression in the hippocampal CA1 subregion of the rats. Results： The expression of nNOS showed moderate and extreme up-regulation in the CIP and ischemia groups, respectively, compared to the sham group. The preceded CIP blocked in certain extent the extreme up-regulation of nNOS induced by brain isehemia in CIP ＋ isehemia group. Administration of MTPG via lateral cerebral ventricle 20 min before CIP blocked the up-regulation of nNOS induced by CIP, but had no influence on the pyramidal neuronal survival. While in the MTPG ＋ CIP ＋ ischemie insult group, the expression of nNOS was stronger than that in the MTPG ＋ CIP group, and the up-regulation was accompanied with obvious delayed neuronal death. Discussion concerned illustrated that the relative intensive up-regulation of nNOS in this group might be attributed to brain ischemia other than MTPG. Conclusion： NO resulted from nNOS participated the induction of mGluR2/3 mediated-brain ischemie tolerance as a downstream molecule of activation of mGluR2/3 during CIP.