氧惊厥时大鼠海马组织一氧化氮合酶基因表达的变化

Changes in the expression of nitric oxide synthase genes in hippocampus of rats with oxygen-induced convulsions

目的探讨一氧化氮合酶基因在氧惊厥发生机制中的作用。方法40只sD大鼠按数字表法随机分为5组：正常对照组、氧惊厥组、惊厥前组、氮氧组、抑制剂＋高压氧（HBO）组，每组8只。氧惊厥组：实验动物放入动物高压氧舱内，用纯氧加压至600kPa，当动物发生惊厥大发作时减压。惊厥前组：纯氧加压至600kPa，动物出现惊厥前期症状时开始减压。氮氧组：动物在含氧3．5％的氮氧混合气下，在600kPa停留30min，再减压。抑制剂＋HBO组：动物进舱前10min腹腔注射L—NAME（N-硝基-三．精氨酸甲酯），其他处理同氧惊厥组。正常对照组：动物置于加压舱内，模拟除压力和氧浓度以外的其他实验条件。各组动物出舱后取海马组织，抽提RNA后，逆转录聚合酶链反应（RT—PCR）测定各组iNOS、nNOS的mRNA表达量变化。结果相对于正常对照组（0．3563±0．1036，0．5625±0．1035），氧惊厥组和抑制剂＋HBO组海马组织中的iNOS（0．5513±0．1253，0．8588±0．1062）和nNOS（0．9300±0．1061，1．2238±0．1374）的表达均显著增加（P〈0．05或P〈0．01）；氮氧组NOS基因表达改变不明显；NOS抑制剂可诱导氧惊厥动物海马组织的NOS基因表达。结论NOS抑制剂可通过不完全阻断NOS的合成，延缓氧中毒的发作及降低发作程度，在氧惊厥发病机制中起重要作用。

Objective To investigate the effect of nitric oxide synthase genes on the mechanism of oxygen-induced convulsions. Methods Forty healthy male Sprague-Dawley rats were chosen at random and divided into 5 groups： the normal control group, the model group （the oxygen-induced convulsions group）, the convulsion group before decompression, the N2-O2 mixture group and the inhibitor ＋ HBO group, each consisting of 8 animals. Rats in the model group were exposed to 600 kPa HBO and decompression was implemented, when convulsive seizures were present. Rats in the convulsion group before decompression were also exposed to 600 kPa HBO and decompression started, before precursor symptoms were present. Rats in the N2- 02 mixture group were exposed to 600 kPa N2-O2 mixture containing 3.5% oxygen for 30min, then they were decompressed. Rats in the inhibitor ＋ HBO group were given an abdominal injection of N-nitro-larginine methylester （L-NAME） 10 minutes before entrance into the chamber. Other treatments were the same as those of the convulsion group. Following decompression to normal pressure, hippocampi of rats were collected and total RNA were prepared by using Trizol Reagent. The expression levels of mRNA in iNOS,nNOS genes in various groups were detected with RT-PCR. Results The expression levels of iNOS and nNOS were all significantly higher tham those of the animals in the convulsion group, when they were compared with those of the normal control group. For the animals in the N2-O2 mixture group, no significant changes could be detected in the expression of NOS genes. NOS inhibitor （L-NAME） could induce the expression of NOS genes in rats with convulsive seizures. Conclusions NOS seemed to play an important role in the pathogenesis of oxygen- induced convulsion. NOS inhibitor could delay the onset of oxygen convulsion and decrease the severity of seizure through incomplete blocking of NOS synthesis.