一氧化氮-环磷酸鸟苷通路对耳蜗灵敏度的调节

目的探讨一氧化氮（NO，nitric oxide）-环磷酸鸟苷（cyclic guanosine monophosphate，cGMP）通路对耳蜗功能的调节。方法健康杂色豚鼠100只，雌雄不限，用随机数字表法随机分为10组，每组10只：①第1组：人工外淋巴液组；②第2组：L-精氨酸组；③第3组：Ca^2＋-ATP酶抑制剂组；④第4组：Ca^2＋-ATP酶抑制剂＋L-精氨酸组；⑤第5组：Ca^2＋-ATP酶抑制剂＋cGMP；⑥第6组：Ca^2＋-ATP酶抑制刺＋L．精氨酸＋非选择性一氧化氮合酶（NOS）抑制剂组；⑦第7组：血管内皮性一氧化氮合酶（eNOS）抑制剂组；⑧第8组：Ca^2＋-ATP酶抑制剂＋eNOS抑制剂组；⑨第9组：Ca^2＋-ATP酶抑制剂＋eNOS抑制剂＋L．精氨酸组；⑩第10组：Ca^2＋-ATP酶抑制剂＋eNOS抑制剂＋L-精氨酸＋神经元性一氧化氮合酶（nNOS）抑制剂组。分别全耳蜗灌流以上各组药物120min，由圆窗龛每隔30min测1次耳蜗微音器电位（cochlear microphonic，CM）和耳蜗听神经复合动作电位（compound action potential，CAP）。第3，4组灌流后留置标本做透射电镜的标本固定。结果第3组灌流Ca^2＋-ATP酶抑制刺前后CAP阈移为28．5dB，第4组在此基础上加入L．精氨酸可使CAP阈移改善9dB，且与加入cGMP后作用相似。第8组多加入eNOS抑制剂抑制血管纹功能后CAP阈移为42．5dB，再加入L-精氨酸可使CAP阈移改善7dB，而第10组加入nNOS抑制剂后CAP阈移较第9组增加了6、5dB，与第8组无明显差异。提示L-精氨酸在nNOS作用下可通过NO-cGMP通路来拮抗Ca^2＋-ATP酶抑制剂引起的胞内Ca^2＋-升高。透射电镜的结果显示：在Ca^2＋-ATP酶抑制剂的基础上加入L-精氨酸减轻了由Ca^2＋-ATP酶抑制剂所造成的外毛细胞的空泡化。结论NO-cGMP通路可调节耳蜗电位，L-精氨酸通过nNOS改善Corti器的功能。

Regulation of nitric oxide-cyclic guanosine monophosphate pathway on cochlear sensitivity

Objective To investigate the effect of nitric oxide (NO) -cyclic guanosine monophosphate (cGMP) pathway on cochlear sensitivity. Methods Ten groups of guinea pigs were treated with the following solutions by whole cochlear perfusion for 2 hours;(1)Artificial perilymph;(2)L-arginine; (3)Ca2+ -ATPase inhibitor;(4)Ca2+ -ATPase inhibitor + L-arginine;(5)Ca2+ -ATPase inhibitor + cGMP;(6)Ca2+ ATPase inhibitor + L-arginine + Non-selective NOS inhibitor; (7)eNOS inhibitor;(8)eNOS inhibitor + Ca2+-ATPase inhibitor;(9)eNOS inhibitor + Ca2+ -ATPase inhibitor + L-arginine;(10)eNOS inhibitor + Ca2+ -ATPase inhibitor + L-arginine + nNOS inhibitor. The compound action potential (CAP) and cochlea microphonics (CM) were measured to assess the changes of cochlear sensitivity. After the perfusion, the cochleae were harvested and prepared for transmission electron microscopy. Results The average threshold shift of CAP after perfusion Ca2+ -ATPase inhibitor was 28. 5 dB, and it was improved in group 4 with 9 dB by L-arginine, similar with group 5. The threshold shift of CAP in group 8 was 42. 5 dB, and it decreased in group 9 by L-arginine, on this foundation nNOS inhibitor was added, increased threshold shift of CAP was 6. 5 dB, similar with group 8. The results indicated that L-arginine could rivalry the role of Ca2+-ATPase inhibitor through the path of NO-cGMP. Transmission electron microscopy showed that Ca2+ -ATPase inhibitor + L-arginine combined administration resulted in less vacuolization in out hair cell than that treated with Ca2+ -ATPase inhibitor only. Conclusions The NO-cGMP pathway could regulate cochlear sensitivity; L-arginine may improve the function of Corti's organ via nNOS, and they indicate an important role of supporting cells in the modulation of cochlear function.