转人P301L突变tau基因小鼠学习记忆功能与与脑内NO的改变

Change of memory function and decrease of nitric oxide level of whole brain in the transgenic mice expressing human tau 40 with P301L mutation

目的:探究第十代转人P301L突变tau基因小鼠(F10)学习记忆障碍的机制。方法:Western blot法检测F10代小鼠人tau蛋白的表达与tau蛋白磷酸化水平的改变;Bielshowsky法银染脑片显示神经纤维缠结;旷场实验与避暗实验检测小鼠学习记忆能力的改变。比色法检测小鼠全脑乙酰胆碱水平,胆碱乙酰转移酶活性与胆碱酯酶活性变化;硝酸还原酶法检测小鼠全脑一氧化氮水平的改变。结果:转人P301L突变tau基因小鼠可表达外源人tau蛋白,3月龄小鼠大脑皮层和海马中出现tau蛋白磷酸化水平明显升高及7月龄小鼠皮层形成神经纤维缠结和出现学习记忆障碍;转人P301L突变tau基因小鼠全脑乙酰胆碱水平,胆碱酯酶活性和胆碱乙酰转移酶活性及表达均未见明显改变;但该小鼠全脑一氧化氮水平却明显下降。结论:F10代转人P301L突变tau基因小鼠仍可遗传亲本性状,7月龄小鼠同时出现学习记忆障碍与全脑一氧化氮含量明显下降的现象,提示转人P301L突变tau基因小鼠全脑一氧化氮含量下降可能涉及其学习记忆障碍机制。

Objective： To study the mechanism of learning and memory dysfuction in the transgenic mouse expressing human tau 40 isoform with P301L mutation （F10）. Methods： The human tau protein expression and phosphor-tau protein levels were detected with Western blot method. The neurofibrillary tangles were observed with Bielshowsky silver stain. The behavior changes of learning and memory were observed by open field test and passive avoidance test. Acetylcholine level, activities of acetycholinesterase and choline acetyhransferase of whole brain was detected by colorimetry method. The nitric oxide level of whole brain was detected by nitrate enzyme reduction method. Results： Exoge-nous human tau gene was expressed and an elevation of phosphor-tan protein level in 7 and 3-month transgenic mice＇ s hippocampus andcere- brocortex was observed. The neurofibrillary tangles were observed in cerebrocortex of 7-month transgenic mice; the 7-month transgenic mice al- so presented an evident reduction of learning and memory ability and nitric oxide level of the whole brain, but not ctmnges in acetylcholine lev- el, acetycholinesterase activity, choline acetyltransferase activity and expression in whole brain. Conclusion： Tau transgenic mice （F10） can still inherit their parents＇ biologiccal characters, and develop learning and memory dysfunction awnodh san obvious decrease in nitric oxide lev- el of whole brain in the 7-month old mice, suggesting a decrease of nitric oxide level of whole brain would be involved in the mechanism of learning and memory dysfunction in these transgenic mice.