化学修饰电极对雏鸡耳蜗神经元一氧化氮的定性检测

目的比较雏鸡和哺乳动物耳蜗生理功能的异同。过去已有哺乳动物耳蜗及前庭神经元中一氧化氮合酶（ＮＯＳ）活动证据的报道，其所释放的一氧化氮（ＮＯ）在听觉和平衡活动中可能发挥重要作用。方法用经化学修饰的碳纤维微电极，定性检测雏鸡离体耳蜗神经元在不同激动剂的诱发下所释放的ＮＯ。根据电极所检测的电流变化的幅度和持续时间判断ＮＯ的释放。结果由激动剂乙酰胆碱和Ｌ精氨酸所诱发的ＮＯ释放反应幅度相似，但乙酰胆碱的高电流持续时间较短，而ＡＴＰ所致者幅度大，持续时间长。预加ＮＧ硝基Ｌ精氨酸，再加上述激动剂，电流无变化。结论雏鸡耳蜗神经元细胞中存在ＮＯＳ。     

雏鸡耳蜗中的一氧化氮合成酶分布

应用冰冻切片组织化学技术，以还原型尼克酰胺腺嘌呤二核苷酸磷酸-黄递酶特异性地确定一氧化氮合成酶（NOS）在小鸡耳蜗中存在，观察其分布情况，发现听毛细胞底部颗粒较集中，染色深，毛细胞周围亦有散在颗粒，基底乳头近端与远端染色强弱相似。阳性反应神经纤维连接毛细胞底部。螺旋神经节细胞胞浆中有大量的蓝色颗粒，细胞核无着色，这些细胞大小均匀，呈圆形或椭圆形，周围有多量阳性神经纤维，提示可能为神经性NOS。血管盖内皮细胞胞浆中酶活性较强。对这些分布特点和意义进行了讨论。     

丹参注射液对庆大霉素耳中毒豚鼠耳蜗一氧化氮生成的影响

目的　研究丹参注射液对庆大霉素 (GM)耳中毒豚鼠耳蜗一氧化氮 (NO)生成的影响 ,探讨丹参注射液对GM耳蜗毒性的防护作用及其作用机制。方法　豚鼠随机分成正常对照组、GM组、GM +丹参组和丹参组 ,应用改良镀铜镉还原法测定豚鼠耳蜗组织中NO含量 ,同时结合听性脑干反应 (ABR)测试 ,观察用药前后听阈变化。结果　GM +丹参组豚鼠耳蜗NO含量和ABR阈值均明显低于GM组 (P <0 .0 1) ;且各组NO含量变化与ABR阈值高度相关 (r正常对照 =0 .96 5 ;rGM=0 .990 ;rGM +丹参 =0 .880 ;r丹参 =0 .980 ;P <0 .0 5 ,P <0 .0 1)。结论　丹参注射液可通过抑制GM引起的NO过量生成 ,以减轻GM的耳毒性损伤 ,从而改善听功能。这可能也是丹参注射液拮抗GM耳蜗毒性的作用机制之一。     

Glutamate toxicity induced degeneration of outer hair cells with a temporal increase of nitric oxide production in the guinea pig cochlea

The aim of this study was to examine the roles of glutamate (GLU) toxicity and involvement of nitric oxide (NO) in the pathogenesis of cochlear degeneration. We examined guinea pig cochleae following chronic exposure to GLU. Trypan blue extrusion and transmission electron microscopy were performed to evaluate degeneration in the organ of Corti. In parallel, nitric oxide synthase (NOS) activity was demonstrated by histochemical staining of NADPH diapholase. GLU treatment caused time-dependent degeneration of outer hair cells (OHCs) in conjunction with a temporal increase of NOS activity in the organ of Corti. This suggests that GLU may be involved in OHC degeneration under toxic conditions, with NO production possibly playing a role in this process. Received: 2 April 1998 / Accepted: 4 December 1998     

Nitric oxide contributes to control of effusion in experimental otitis media

OBJECTIVES/HYPOTHESIS: Nitric oxide (NO) is a small, short-lived free radical involved in cellular signaling and known to play a role in inflammation. It is generated on demand by the enzyme nitric oxide synthase (NOS) on arginine. We have previously found that mRNA encoding NOS is produced in the middle ear during otitis media. The role of NO was therefore explored in an experimental model of immune-mediated otitis media. STUDY DESIGN AND METHODS: Guinea pigs were systemically immunized and later challenged in the middle ear with the same antigen. One ear of each animal was challenged with antigen alone. In the opposite ear, antigen was combined with a potent inhibitor of NOS, N(G)-amino-L-arginine (L-NAA). After survival for 24, 48, or 72 hours, the middle ears were evaluated for otitis media. RESULTS: Inhibition of NOS resulted in significantly increased middle ear effusion at all three time periods. This increase was blocked by the addition of excess 1-arginine, which bypasses the inhibitory effects of L-NAA. The infiltration of cells into the middle ear lumen and the hyperplasia of the middle ear mucosa were unaffected by L-NAA administration. CONCLUSIONS: The results suggest that NO is involved in regulating the permeability of the middle ear vascular, the transudation of serum into the middle ear mucosa, and/or the movement of extracellular fluid across the middle ear mucosal epithelium.     

一氧化氮合酶和心钠素在豚鼠耳蜗的分布

目的 观察豚鼠耳蜗局部心钠素（atral natruretc peptde，ANP）和一氧化氮合酶（nitric oxide synthase，NOS）免疫组化反应产物的分布，为研究ANP和NOS在豚鼠耳蜗局部血流、淋巴以及神经调节中的相互作用提供形态学依据。方法 采用免疫组织化学双标法检测ANP和NOS在正常豚鼠耳蜗的分布特征。结果 在耳蜗各转螺旋动脉和血管纹．螺旋缘、螺旋韧带和Corti器显示双阳性染色，螺旋神经节细胞及囊斑神经上皮细胞膜及轴突NOS阳性染色，胞质ANP阳性染色；盖膜、前庭膜阴性染色。结论 ANP和NOS在内耳血 流调节，内、外淋巴平衡调节以及神经信号传递等方面可能具有重要作用，二者之间可能存在密切的相互作用机制，其分布特点与功能密切相关。     

Nitric oxide mediates capsaicin-induced increase in cochlear blood flow

Capsaicin has been previously shown to increase cochlear blood flow (CBF) in a dose-dependent manner. The aim of this study was to define the role of nitric oxide (NO) in capsaicin-induced changes in CBF. This was investigated in the anesthetized guinea pig, utilizing laser Doppler flowmetry. Application of capsaicin (64.8 and 6.48 nmol in 2 μl of saline) to the round window membrane (RWM) caused increases in CBF (34 ± 2.8% of baseline (BL) and 28 ± 2.3% BL, respectively (P < 0.001)). Application of the NO synthase inhibitor, N^G-nitro-l-arginine methyl ester (l-NAME) (10 mg/kg intravenously or topically to the RWM) reduced blood flow in the cochlea, as previously reported. After pretreatment with i.v. l-NAME, the effect of capsaicin on CBF was significantly decreased. With the dose of capsaicin at 64.8 nmol, the increase in CBF fell from 34 ± 2.8% BL to 6.9 ± 1.5% BL (P < 0.001), and at 6.48 nmol it fell from 28 ± 2.3% BL to 4.8 ± 1.6% BL (P < 0.001). RWM l-NAME application also decreased the capsaicin vasodilatation effect. A capsaicin dose of 64.8 nmol resulted in only a 10 ± 2.5% BL increase in CBF, and with 6.48 nmol capsaicin the increase was 7.8 ± 2.2% of BL (P < 0.001). Capsaicin-sensitive sensory neurons in other systems are generally known to release substance P (SP), which in turn elicits release of endothelium derived relaxing factor (NO). The results of this study indicate that NO is a mediator of capsaicin-sensitive sensory neuronal function in CBF regulation.     

Nitric oxide synthase inhibitor reduces noise-induced cochlear damage in guinea pigs

Conclusion. The results obtained in this study indicate that N^G-nitro-L-arginine methyl ester (L-NAME) protects cochlear damage from acoustic trauma through reducing the production of nitric oxide (NO). Objectives. This study aimed to explore whether NO synthase inhibitor L-NAME could reduce cochlear damage in acoustic trauma. Materials and methods. Seventy guinea pigs (300–350g) were divided randomly into four groups (n=20 in groups I, III, and IV; n=10 in group II). Two days consecutively and 30min before noise exposure (4kHz octave band, 115dB SPL 5h), subjects received an injection of 5ml saline/kg (groups I and III) or 10mg/kg L-NAME (groups II and IV). Sham-exposed guinea pigs were listed as groups I and II. Protection was assessed physiologically by the change in auditory brainstem response (ABR) threshold and histologically by survival of outer hair cells (OHCs). NO level of cochlear tissue was assayed 3days after noise exposure. Results. Group III showed significantly greater OHC loss, threshold shifts and NO level compared with group I and group IV. Compared with group III, noise-induced elevation in NO level in the cochlea was significantly attenuated by L-NAME (p<0.001).