窒息对不同龄豚鼠耳蜗生物电的影响

应用微电极技术，观测内耳实验中常用两组不同龄豚鼠及恢复供氧过程中蜗内电位（ＥＰ）、微音电位（ＣＭ）、总和电位（ＳＰ）的变化，发现大龄豚鼠于窒息时ＥＰ下降较小龄豚鼠慢，＋ＳＰ的峰值大，恢复供氧后ＥＰ、ＣＭ的回升快，－ＳＰ的峰值亦大，提示大龄鼠的血管纹、外毛细胞、内毛细胞均较小龄鼠成熟。     

豚鼠耳蜗和内淋巴囊水通道蛋白的表达

目的 研究豚鼠耳蜗和内淋巴囊组织中水通道蛋白(aquaporin，AQP)不同亚型的定位表达及其意义。方法 用兔抗大鼠AQP1、AQP2、AQP3、AQP4的多克隆抗体，采用免疫组化SP法分别检测相应AQP蛋白亚型在豚鼠耳蜗和内淋巴囊组织中的表达模式。结果 在耳蜗组织中，AQP1、4广泛分布于耳蜗的各个区域，如血管纹、螺旋韧带、Corti器、螺旋缘、螺旋神经节等，AQP3除了在血管纹表达呈弱阳性外，其余区域的表达与AQP1和AQP4相似，AQP2则仅表达于Reissner膜。在内淋巴囊组织中，AQP1、AQP3和AQP4在内淋巴囊上皮细胞和上皮下纤维组织均呈强阳性表达，只是AQP3的表达强度稍弱于AQP1和AQP4，而AQP2在内淋巴囊上皮细胞和上皮下组织均呈阴性表达。结论 水通道蛋白1、3、4以相似的方式广泛分布于豚鼠耳蜗和内淋巴囊组织中，而AQP2则仅表达于Reissner膜，提示不同亚型的AQP可能在不同区域协同作用参与内淋巴的调节，从而保持内耳内环境的稳定。     

过氧化氢对豚鼠耳蜗功能及形态的影响

目的 在体观察过氧化氢(H2O2)对豚鼠耳蜗功能及形态的影响。方法 实验动物分为4组，分别灌流人工外淋巴液(artificial perilymph,APL)，50μMH2O2，100μMH2O2和200μMH2O2(H2O2均溶于APL中)，并用Pl和H033342双染色方法观察H2O2引起的内耳细胞损伤情况。结果 所有H2O2灌流组复合动作电位((CAP)阈移和耳蜗微音电位(CM)幅度变化与人工外淋巴液组比较差异有显著性，且各H2O2组的变化呈现出浓度依赖性；Pl和H033342双染色方法发现外毛细胞是H2O2攻击的主要靶细胞，而Hensen细胞未见任何损伤痕迹。结论 H2O2可导致耳蜗功能下降及耳蜗毛细胞损伤：Hensen细胞较毛细胞可能具有更强的抗氧化能力。     

噪声对豚鼠耳蜗电位及其超微结构的影响

目的观察噪声暴露对豚鼠耳蜗电位和超微结构的影响。方法选用健康杂色豚鼠10只,以右耳为噪声暴露耳,以左耳为对照耳,右耳持续给白噪声100dBSPL2小时。于噪声暴露前及噪声暴露后测量右耳耳蜗电位,并于噪声暴露后取噪声暴露耳和对照耳的耳蜗,应用透射电镜进行形态学的观察。结果噪声暴露后耳蜗微音电位幅度下降并且其非线性特点消失,听神经复合动作电位阈值明显升高;内毛细胞及其下方传入神经末梢空化,外毛细胞溶酶体增多、胞浆内出现空泡。结论噪声暴露不仅引起外毛细胞的损伤,还可以引起内毛细胞及传入神经纤维的损伤。     

豚鼠耳蜗和内淋巴囊上皮钠通道的表达

目的 研究豚鼠耳蜗和内淋巴囊组织中上皮钠通道(epithelial sodium channel,ENaC)α、β、γ亚基的表达及其意义.方法 用兔抗大鼠ENaC α、β和γ亚基的多克隆抗体,采用免疫组化SP法观察豚鼠耳蜗和内淋巴囊组织中α、β、γ-ENaC的表达模式.另用α-ENaC cDNA质粒合成探针,原位杂交法检测豚鼠耳蜗和内淋巴囊组织中α-ENaC mRNA的表达.结果 免疫组化显示,在豚鼠耳蜗中,α-ENaC蛋白强烈表达于螺旋缘,而螺旋韧带、Corti器、Reissner膜等处的表达较弱;β-ENaC蛋白在螺旋韧带、螺旋缘和螺旋神经节、Corti器、Reissner膜等处的表达均呈弱阳性;γ-ENaC蛋白则在螺旋韧带的上半部、螺旋缘和螺旋神经节等处的表达呈强阳性,Corti器、Reissner膜等处也有阳性表达.三个亚基在血管纹中均呈阴性表达.在内淋巴囊中,α、β和γ亚基均较明显地表达于上皮细胞和上皮下纤维组织.原位杂交显示,α-ENaC mRNA除了表达于螺旋缘、螺旋韧带下部外,还表达于血管纹,而在内淋巴囊的上皮细胞和上皮下纤维组织也均呈阳性表达.结论 ENaC的各个亚基以不同的模式分布于豚鼠耳蜗和内淋巴囊的各个区域,形成功能性通道参与内淋巴的调节,从而保持内耳内环境的稳定.     

蜗内直流电对耳蜗基底膜振动的影响

目的：探讨外加直流电流后对耳蜗基底膜振动的影响。方法：在豚鼠耳蜗底回距圆窗龛缘2．4mm处开一直径约0．4mm小孔，作为测量活体基底膜的振动速度测试窗，在测试窗上，下缘的鼓阶，前庭阶各开一小孔，将铂－铱电极置入鼓阶，前庭阶作为跨蜗管的电刺激电极，用激光多普勒干涉测速仪观察直流电流对纯音诱发的基底膜振动速度的影响。结果：当外加电流前庭阶极性为正，鼓阶极性为负时，可以看到基底膜振动速度显著增大，给相反极性电流时，基底膜振动速度减小。结论：生理状态下的正内淋巴电位是耳蜗将声音能量转变为神经冲动的必要条件，适当提高外毛细胞顶端正电位，有助于提高耳蜗放大器的增益，外加负电位则严重影响耳蜗放大器的增益。     

内淋巴囊直流电位的因素,作用及其机制研究进展

本综述了近年来有关内淋巴囊直流电位（ＥＳＰ）的研究进展，着重对ＥＳＰ的影响因素、作用及其机制作了阐述。这对深入研究内淋巴囊电生理具有重要意义。     

豚鼠耳蜗微血管铸型的扫描电镜观察

应用血管铸型技术和扫描电镜观察了豚鼠耳蜗的微血管，结果见耳蜗血管均被铸型物完全充填，耳蜗血管的总体三维空间图像得以清晰地显示。作者对外放射状动脉及其分支，以及耳蜗侧壁回流静脉的解剖进行了仔细观察。     

豚鼠耳蜗微血管的形态学观察

应用光镜、透射电镜和扫描电镜结合苯乙稀包埋割断技术，联合观察豚鼠耳蜗微血管的形态学结构。结果表明，血管纹和螺旋韧带毛细血管为连续型内皮细胞。这些连续型毛细血管以及内皮细胞之间的紧密连接构成了耳蜗血－迷路屏障重要的形态学基础。并对有关的耳蜗微血管的血流动力学循征进行了讨论。     

强脉冲噪声对豚鼠耳蜗血管纹血管的影响

强脉冲噪声暴露后,用耳蜗电图记录CAP和-SP,光镜观察耳蜗毛细胞损伤情况,图象分析法定量测定耳蜗血管纹血管的管腔面积及红血球分布。结果提示,爆震后即刻,耳蜗各圈毛细胞血管明显扩张、充血,爆震后4天恢复至正常范围,CAP阈移以4kHz、8kHz最大,与外毛细胞损伤主要位于1T、2T基本吻合,但与血管纹血管变化并不协调对应,似说明耳蜗微循环的改变与毛细胞的损伤无直接关系。     

The effect of adenylate cyclase stimulation on endocochlear potential in the guinea pig

Summary Forskolin, a diterpene extracted from Coleus forskohlii, is potentially an important tool for studying the modulation of ionic currents by cAMP because it stimulates adenylate cyclase in a variety of cells. We studied the effect of forskolin on cochlear potentials and found that its perfusion of the scala vestibuli (SV) to a concentration more than 10^–5 M and the scala tympani (ST) to more than 10^–4 M produced a reversible elevation of the endocochlear potential (EP) in a dose-dependent manner. The cochlear microphonics recorded simultaneously with the EP was not depressed during the EP elevation. A large negative EP was induced by anoxia following the SV perfusion with forskolin (2 × 10^–4 M). The results suggest that the EP elevation produced by forskolin does not result from the decrease in the negative component of EP but from the increase in the positive component of EP.Presented at the 25th Workshop on Inner Ear Biology in London, England, 4–7 September 1988     

Susceptibility of the endocochlear potential to pH and osmolarity changes in the perilymph of the cochlea in the guinea pig

Summary The effects of artificial perilymph at various pH levels and osmolarities on the endocochlear potential (EP) were investigated in a guinea pig model. In 47 ears, the mean EP was 74.5 ± 0.5 mV in the second turn of the cochlea before perilymphatic perfusion. The artificial perilymph with a pH ranging from 5 to 9 and tonicity less than 1.25 (osmolarity, 345 mosmol/1) did not alter the EP when testings were recorded for at least 1 h. However, after the start of a perfusion with a pH less than 4, the EP declined gradually but recovered to the pre-perfusion level rapidly when the perfusion was stopped. The artificial perilymph with a pH over 10 decreased the EP considerably but showed no recovery, even after cessation of the perfusion. Tonicity more than 1.35 (osmolarity, 372.6 mosmol/1) also decreased the EP, with this decrease paralleling further increases in the tonicity used. From these data, we have concluded that a perilymph perfusate with a pH from 5 to 9 and an osmolarity less than 350 mosmol/I can be used in animal testing without any noxious effects on the EP.Offprint requests to: S. Wakizono     

Effects of anoxia on the cochlear summating potential in the guinea pig

Summary The cochlear summating potential (SP) was recorded extracochlearly from the apex and the round window in 25 guinea pigs, applying anoxia during periods of 1–2 min. For 2 and 8 kHz tone pips at 80 and 60 dB SPL, respectively, the initially negative SP at the apex diminished and even became positive during oxygen cut-off. After restoration of oxygenation, the change in SP reversed direction and was followed by a large negative undershoot. At the round window, the initially positive SP evoked by 8 kHz, 60 dB SPL tone pips followed exactly the same time course, but with inverted polarity, while the majority of the recordings of the initially negative SP evoked by 2 kHz, 80 dB SPL tone pips followed a course similar to the apical negative SP. However, the negative round window SP showed only slight polarity reversal and no undershoot. A small number of the recordings at the round window for 2 kHz showed an increase of the negative SP during anoxia followed by a decline of the SP and recovery after anoxia. The similar time course of the initially negative SP at the apex and the initially positive SP at the round window failed to support the hypothesis of a multi-component SP. However, the polarity reversal during anoxia and the different reactions to anoxia of the 2 kHz round-window SP suggest that the SP may consist of several different components.     

Mechanism of lack of development of negative endocochlear potential in guinea pigs with hair cell loss

The endocochlear potential (EP), and the concentration of K⁺, Na⁺ and Cl⁻ were measured simultaneously in endolymph of guinea pigs. The EP was 85.6±0.8 mV in normal guinea pigs, 90.7±0.8 mV in the kanamycin-treated animals, and 91.6 ±1.2 mV in those treated with nitrogen mustard-N-oxide (NMNO). Thirty minutes after the onset of anoxia, the EP (negative EP) was −29.3 ± 1.0 mV in the normal group, −0.2±1.0 mV in the kanamycintreated group, and −1.9±1.3 mV in the NMNO-treated group. The permeability coefficients of K⁺ (P_k), Na⁺ (P_na) and Cl⁻ (P_cl) across the endolymph-perilymph barrier during the period of 20–30 min after the onset of anoxia in the normal group were (341.6±38.2) × 10⁻⁹ cm³ sec⁻¹, (53.0±8.1) × 10⁻⁹ cm³ sec⁻¹ and (111.8±27.2) × 10⁻⁹ cm³ sec⁻¹, respectively. P_k was decreased in the kanamycin- and NMNO-treated groups. P_na did not differ between the normal and treated groups. P_cl was increased in the kanamycin- and NMNO-treated groups. The K⁺:Na⁺:Cl⁻ permeability ratio was 1:0.16:0.32 in the normal group, 1:1.12:11.6 in the kanamycin-treated group, and 1:0.44:5.60 in the NMNO-treated group. The results indicate that the lack of development of a negative EP in the kanamycin- and NMNO-treated guinea pigs was attributable to the increased P_cland the decreased P_k across the endolymph-perilymph barrier, probably the organ of Corti. during anoxia.     

耳前入路小型猪耳蜗内电位的测定的研究

目的 研究正常小型猪中耳及内耳解剖及耳前入路耳蜗内电位测定的可行性,为以小型猪作为动物模型的内耳数据测定及内耳疾病治疗提供实验基础和解剖学依据.方法 10只正常1周龄贵州香猪,麻醉后测量ABR确定听力正常,测听后分为2组,实验组(7只),以耳前入路进行中耳及内耳解剖,对照组(3只)以腹侧入路进行解剖.充分暴露耳蜗.分别测量每只小型猪左侧耳蜗内电位,观察正常小型猪的耳蜗内电位的范围.术后1天观察小型猪的基本生物学特征.结果 实验组小型猪7耳中4耳测出稳定的耳蜗内电位；对照组3耳仅有1耳测出.术后1天实验组小型猪生命体征均平稳,正常饮食；对照组中1只术中死亡,其余术后状态欠佳.结论 对于小型猪而言,耳前入路操作简单、损伤小、易于暴露圆窗龛,能够顺利完成耳蜗内电位的测定.     

Differences in endocochlear potentials in response to anoxia in maturing and mature guinea pigs

Summary Endocochlear potential (EP) responses to anoxia in immature and mature guinea pigs were compared. The EP decreased much more slowly after anoxia in guinea-pig embryos than in neonates. In many of the embryos, the EP failed to reach any negative voltage. These findings show that the development of the negative component of the EP is a function of the maturation of its positive component.Presented at the 26th Workshop on Inner-Ear Biology in Paris, France, 3–6 September 1989     

Prolonged maintenance of endocochlear potential by vascular perfusion with media devoid of oxygen carriers

Summary A method is described for maintaining the cochlear potentials of the guinea pig via arterial perfusion of the surviving inner ear with an artificial medium devoid of oxygen carriers or oncotic agents. The endocochlear potential (EP) can be maintained at a normal level for periods in excess of 5 h; the responses of the EP to anoxia and to furosemide closely approximate those seen in the intact animal. This preparation may represent a simplified method for carrying out selected arterial perfusion experiments in the surviving inner ear.Supported by NIH grant NS 06575 and NSF grant BNS-8118772     

Dissociation of the cochlear microphonics and endocochlear potential after injection of ethacrynic acid

Summary The cochlear microphonics (CM), endocochlear potential (EP) and summating potential (SP) were simultaneously recorded for 60 min after injection of 30 mg/kg body weight of ethacrynic acid. The EP decreased parallel with the CM for about 20 min after injection, but they differed in the recovery stage. Even when the EP was still negative, the output of CM for 500 Hz acoustic stimulus recovered to its original level and was supernormal. A large SP observed in the recovery stage of CM and EP seemed to suggest that some functional change in the hair cells might be connected with the supernormal CM. Four minutes of anoxia during the supernormal CM decreased CM to only 68% of its level prior to anoxia. A cathodal polarization of the scala media, to change the polarity of the dc potential gradient, reversed the polarity of CM in the anoxic guinea-pig cochlea but not in the guinea-pig cochlea administered ethacrynic acid. These results suggest that supernormal CM observed in this experiment may not be dependent on the dc potential gradient, but due to some functional change in the hair cells after the injection of ethacrynic acid, although CM is essentially dependent on the dc potential gradient between the scala media and the inside of the hair cells.     

A method for changing the avian endocochlear potential by current injection

Summary The endocochlear potential (EP) in the pigeon was found to be +10 ± 3 mV. A method for changing the EP by current injection into the scala media is described. The EP change brought about was 1.6–2.9 mV/A and was dependent on the distance from the tip of the current electrode. Single fiber activity in the cochlear ganglion could be recorded simultaneously with the current injection. These experiments have shown that decreases in the EP reduce the sound-evoked activity of primary afferent nerves and elevate their threshold.Presented at the 26th Workshop on Inner Ear Biology in Paris, France, 3–6 September 1989