左旋精氨酸对大鼠大脑皮质和海马α7 nAChR表达的影响

Effects of L-arginine on α7nAChR expressions in cerebral cortex and hippocampus in rats

目的:探讨不同时间应用一氧化氮(nitric oxide,NO)前体左旋精氨酸(L-arginine,L-Arg)对大鼠学习记忆功能及大脑皮质和海马α7烟碱型乙酰胆碱受体(nicotinic acetylcholine receptor,α7 nAChR)表达的影响。方法:Wistar雄性大鼠随机分为6组,分别为连续3、7和14 d侧脑室注射L-Arg(0.5μmol/d,每日1次)的3个实验组,和在相同时间给予同剂量生理盐水的3个对照组。用Y型迷宫刺激器对大鼠进行学习和记忆能力的行为学检测;用NO试剂盒和免疫组化分别检测大鼠大脑前额叶皮质和海马NO含量以及α7 nAChR的表达。结果:大鼠的学习和记忆行为能力、大脑前额叶皮质和海马NO含量以及α7 nAChR阳性细胞数,在三个实验组分别与各自对照组比较均明显增加;在3个实验组之间比较,7 d组较3 d组,14 d组较7 d组比较均明显增加。3个时间点的对照组之间相比较上述指标均没有明显差异。结论:大鼠学习记忆行为改善以及大脑前额叶皮质和海马NO含量和α7 nAChR的表达随着应用L-Arg的延长而增加,NO对学习记忆的影响具有时间依赖性。

Objective： To explore the effects of different time application of nitric oxide （NO） precursor L-arginine （ L- Arg） on the expressions of α7 nicotinic aeetyleholine receptor （ot7nAChR） in cerebral cortex and hippoeampus in rats. Methods： Wistar rats were divided into six groups. Three experimental groups were intracerebroventricularly （i. c. v） injeered with L-Arg（0.5 pLmol/d, once daily） for three days, seven days or fourteen days, respectively; and three control groups were i. c. v injected with the same amount of normal saline during the same periods. The learning and memory abil- ity of rats were tested with Y-maze, the levels of NO and otTnAChR in frontal cortex and hippoeampus were measured with NO assay kit and immunohistochemistry. Results： The learning and memory behavioral responses of rats, and the NO lev- els along with the otTnAChR-like immunoreactive （otTnAChR-LI） cells in prefrontal cortex and hippocampus were signifi- cantly improved in three experimental groups as compared with control groups; and were significantly increased in 7- day L-Arg group as compared with 3- day L-Arg group or in 14- day L-Arg group as compared with 7- day L-Arg group. The above indicators showed no differences in three control groups. Conclusions： The rats＇ ability of learning and memory, the NO levels and the expressions of α7nAChR in prefrontal cortex and hippocampus increased with the extensions of the application of L-Arg. The effect of multiple application of NO on learning and memory might be in a time-dependent manner.