缺氧复氧时培养的大脑皮质神经细胞一氧化氮动态变化及银杏叶提取物的调节作用

本研究用原代混合培养的 Wistar胎鼠大脑皮质神经细胞 ,给予不同时间的缺氧复氧 ,观察其一氧化氮的代谢中间产物亚硝酸盐的动态变化以及诱导型一氧化氮合酶抑制剂氨基胍和银杏叶提取物对一氧化氮的调节作用。结果表明 :缺氧复氧可造成培养大鼠的大脑皮质神经细胞一氧化氮双相升高。即 :在缺氧早期 (缺氧 2 h)可见一氧化氮一过性升高 ,然后很快恢复至正常水平 ;在缺氧 8h、复氧 18h后可见第二次一氧化氮升高。于缺氧前 1h在细胞培养上清液中分别加入氨基胍 (0 .5 m mol/L)和银杏叶提取物 (5 0 μg/ml) ,发现氨基胍可有效地抑制缺氧复氧晚期培养的大鼠大脑皮质神经细胞一氧化氮升高 ,但不能抑制缺氧早期一氧化氮的产生 ;而银杏叶提取物可有效地抑制缺氧复氧诱导的一氧化氮双相升高。提示 :在混合培养的胎鼠大脑皮质神经细胞缺氧复氧损伤模型中 ,一氧化氮的双相升高是由不同亚型的一氧化氮合酶所介导 ,其早期升高可能为神经元型一氧化氮合酶活性上调所致 ,而其晚期升高则是诱导型一氧化氮合酶活性增强的结果 ;银杏叶提取物可抑制缺氧复氧时神经元型和诱导型一氧化氮合酶的活性从而降低一氧化氮的产生而完成其神经保护作用

DYNAMIC CHANGES OF NITRIC OXIDE OF THE CULTURED CORTICAL NEURONAL CELLS FOLLOWING HYPOXIA-REOXYGENATION AND ITS REGULATION BY GINKGO BILOBA EXTRACT

To look into the dynamic changes of nitric oxide (NO) of primary cultured rat cortical neuronal cells induced by different period of hypoxia-reoxygenation (HR) and the effects of inducible nitric oxide synthase inhibitor Aminoguarnidine (AG) as well as Ginkgo biloba extract (EGB) on NO production, an in vitro HR model was established by putting the primary cultured rat cortical neurons to 5% CO 2/95%nitrogen for 2, 4, 6, or 8 hours respectively and then resuscitating to the normal culture condition for another 0 or 18 hours (Being referred as H 2R 0, H 4R 0, H 6R 0, H 8R 0, H 2R 18 , H 4R 18 , H 6R 18 , H 8R 18 group respectively). NO production was measured by detecting NO metabolite nitrite (NO 2 ) by fluorospectrophotometry. The results were as follows: (1) A bi phasic increase in NO production was seen in our experiment following HR. NO production was increased in H 2R 0 group (P<0.05, early phase) and H 8R 18 group (P<0.05, later phase) comparing to the control group. (2) The blockage of the later phase but not the early phase of NO production was seen when the cultured neuronal cells were pre incubated with iNOS inhibitor AG (0.5 mmol/L), indicating that nNOS was responsible for the early phase of NO production, while iNOS activation resulting in the later phase of NO production. (3) The bi phasic increse in NO production was effectively blocked by incubation with EGB (50 μg/ml) one hour before HR. The above results suggested that the protective effect of EGB on neuronal cell death could be due to its inhibition of nNOS and iNOS activity therefore to reduce NO production following HR in this model.