卡铂及其耳毒性

卡铂作为一种铂制剂广泛应用于临床抗肿瘤的化学治疗，其毒副作用主要包括耳毒性，肾毒性，神经毒性．和抑制骨髓造血系统等等。卡铂可以选择性破坏灰鼠的耳蜗内毛细胞和前庭I型毛细胞以及与之相联系的传入神经元。在卡铂引起的灰鼠单纯内毛细胞部分损害动物模型，动物具有正常的耳声发射和微音器电位以及听神经动作电位阈值．但总和电位和听神经动作电位的振幅却明显减小。在卡铂造成60％-90％的内毛细胞缺损的动物模型中，灰鼠在安静条件下对纯音的听觉条件反射阈可以保持正常，但在宽带或窄带噪声的掩蔽作用下，其纯音听觉反射阈值却明显提高，同时对听觉瞬时清晰度的辨别能力也明显降低。卡铂引起的内毛细胞和前庭I型毛细胞及其传入数据元的破坏过程往往伴随着钙激活蛋白酶的活动和Caspase-8的启动以及p53的过度调控从而引起细胞凋亡，同时可见琥珀酸脱氢酶，钠钾ATP酶，碱性磷酸酶和葡萄糖-6-磷酸酶活性的减弱以及钙激活ATP酶活性的增强。无论在灰鼠的活体动物实验还是离体培养条件下．卡铂都对灰鼠耳蜗内毛细胞和前庭I型毛细胞具有特殊的选择性破坏作用。卡铂对灰鼠听觉系统的损害除了导致内毛细胞和I型螺旋神经节凋亡之外。还会破坏耳蜗核神经元。但对下丘和听皮层的神经元却不造成致命性损坏。在耳蜗内毛细胞和I型螺旋神经节以及耳蜗核神经元被卡铂破坏之后．下丘和听皮层神经元对微弱的输入声刺激信号却表现出超乎寻常的敏感性提高。提示中枢神经元可能通过降低其某些抑制性神经递质的释放使神经元的活动代偿性增强．亦可能通过加强兴奋性神经递质的释放．或者通过神经元新长出的轴突和末梢而接受到更多的刺激信号，从而弥补了因周边听觉输入信号减弱而引起的听功能障碍，因此，卡铂耳中毒灰鼠模型还可成为一个研究听觉中枢重组现象或听神经病的理想实验动物模型。     

正常大鼠听觉中枢四种氨基酸类神经递质测定

目的探讨并比较听觉中枢四种氨基酸类神经递质的含量。方法选取成年SD大鼠20只,采用日立835-50型氨基酸自动分析仪分别测定其耳蜗核、下丘和听皮层中r-氨基丁酸(gamma-aminobutyric acid,GABA)、甘氨酸(glycine,Gly)、谷氨酸(glutamic acid,Glu)及天冬氨酸(aspartate,Asp)的含量。结果听皮层与耳蜗核相比,GABA的含量差异无统计学意义(P>0.05),听皮层、耳蜗核分别与下丘相比,其含量差异均有显著统计学意义(P<0.01);听皮层与下丘相比,Gly的含量差异无统计学意义(P>0.05),听皮层、下丘分别与耳蜗核相比,其含量差异均有显著统计学意义(P<0.01);下丘与耳蜗核相比,Glu的含量差异无统计学意义(P>0.05),下丘、耳蜗核分别与听皮层相比,其差异均有显著统计学意义(P<0.01);听皮层、下丘及耳蜗核三者间相互比较,Asp的含量差异均无统计学意义(P>0.05)。结论听觉中枢的不同部位GABA、Gly及Glu的含量各异,可能与其神经元的活性不同有关,反映了脑神经元的功能状态。     

外周听器损伤所致听觉中枢改变的研究进展

耳蜗核、上橄榄核复合体、外侧丘系、下丘共同组成听觉脑干中枢.下丘是耳蜗与大脑之间听觉信号传输的重要中转站,解剖位置恒定,易于定位和进行电生理记录,是研究皮层下听觉中枢功能的重点.本文拟就正常下丘神经元对纯音刺激的反应特点,以及外周听器损伤后下丘神经元的生理学改变和神经递质改变等研究进展进行综述.     

应用FLIVO探测顺铂引起的多器官细胞凋亡

顺铂是一种用于治疗恶性肿瘤的有效铂类化疗药物。然而顺铂对机体许多组织器官,如肾脏、肝脏、神经系统以及内耳等都具有毒性损害作用。FLIVO是一种能够穿越机体组织屏障进入到机体每个细胞并用荧光标记处于凋亡活动状态半胱天冬酶的亲脂性注射用示踪剂。本研究应用袢利尿剂(利尿酸钠,40mg/kg,Ⅰ.V.)暂时性破坏南美栗鼠的血-迷路屏障,促使顺铂(0.8 mg/kg,I.P.)经蜗管外壁屏障消除处进入耳蜗从而引起耳蜗毛细胞凋亡。受试南美栗鼠在联合应用利尿酸钠和顺铂后6小时和18小时终止实验。为了检测顺铂引起的发生在耳蜗和中枢以及肝肾等器官的细胞凋亡,在终止实验前经颈静脉注入100μlFLIVO探测液体并使之随着血液循环60分钟以探测出现在全身各个脏器的凋亡细胞。终止实验时,对麻醉动物常规施行心脏灌流磷酸盐缓冲液5分钟,再经心脏灌流10%福尔马林磷酸盐固定液,然后分别取出耳蜗、耳蜗核、听皮层、海马以及肝肾组织并浸入上述固定液继续固定6小时。在解剖显微镜下分离取出全耳蜗基底膜并制备成全耳蜗基底膜铺片,耳蜗核、听皮层、海马、肝脏和肾脏则常规制备成冰冻切片。在共聚焦显微镜下,观察FLIVO在上述各个器官标记出的凋亡细胞。在正常南美栗鼠各个组织器官中,均未发现FLIVO标记的凋亡信号;在用药后6小时,仅在耳蜗外毛细胞及肾组织中检测出凋亡细胞,但在其它器官也未发现FLIVO标记的凋亡细胞;与用药后6小时相比,在用药后18小时,所有的耳蜗外毛细胞和耳蜗底回大部分内毛细胞都呈现出荧光标记的凋亡信号,出乎意料的是,尽管耳蜗腹侧核神经元出现了大量凋亡神经元,但耳蜗背侧核的神经元却未检测到明显的凋亡信号;值得注意的是,凋亡信号还出现在更为核心的中枢海马神经元和听皮层神经元。此外,肾脏组织和肝脏组织在用药后18小时也出现大量的凋亡细胞。这些结果表明,联合应用利尿酸钠和顺铂不仅导致大量耳蜗毛细胞凋亡,而且顺铂的神经毒性作用还造成了耳蜗腹侧核大量神经元的凋亡和耳蜗背侧核和海马及听皮层的部分神经元凋亡,顺铂同样导致大量的肾脏细胞和肝脏细胞凋亡,出现在上述各个脏器的细胞凋亡现象与顺铂的耳毒性作用、神经毒性作用、肾毒性作用及肝毒性作用完全一致。     

耳蜗急性纯音损伤后下丘及耳蜗核快速功能重组

实验比较高强度纯音损伤耳蜗局部区域前后，耳蜗背核及下丘接近损伤区边缘的神经元反应特性的改变。致损纯音的频率高于神经元的特征频率，且位于其兴奋区以外，所以不影响其兴奋性输入。结果发现此种纯音损伤在逾半数的神经元产生不同程度的去抑制效应，提示皮层的功能重组可能部分地起源于低位中枢的功能改变，下丘和耳蜗背核的抑制性神经网络具有相当程度的侧抑制组分。     

大鼠单侧耳蜗损毁后下丘r-氨基丁酸及其神经元的变化

目的：研究大鼠单侧耳蜗损毁前后不同时期,下丘中r-氨基丁酸（gamma-aminobutyric acid,GABA）含量及其阳性神经元的分布变化,初步探讨去传入损伤后GABA在听觉中枢重组中的作用和意义。方法：健康SD大鼠随机分为4组：正常组和单侧耳蜗损毁后1周、2周及1个月组。于规定时间内检测并比较耳蜗损毁前后GABA含量及其阳性神经元的数量。结果：与正常组相比,损毁后1周,下丘中GABA含量及其神经元数量明显下降,差异有统计学意义（P〈0．05）;术后2周,下丘中GABA含量及其神经元数量稍上升但仍低于正常组（P〈0．05）;至术后1个月,下丘中GABA含量及其神经元数量上升,与正常组比较差异均无统计学意义（P〉0．05）。结论：单侧耳蜗损毁后,GABA含量及其阳性神经元数量在下丘中呈一明显的动态变化过程,说明GA—BA作为一种神经递质参与了耳蜗毁损后听功能的重组过程,提示GABA在单侧耳蜗损毁后听觉中枢的重组过程中可能起重要作用。     

内毛细胞缺损对噪声引起外毛细胞损害的潜在影响

目的　观察噪声对正常灰鼠和内毛细胞缺损灰鼠的外毛细胞是否具有不同的破坏效应。方法　 6只正常灰鼠和 12只卡铂致聋灰鼠作为受试对象。提前 30天给 12只灰鼠按照 10 0mg/kg的剂量腹腔注射卡铂 ,以达到预先选择性破坏其内毛细胞的目的。将 6只正常灰鼠和 6只经卡铂处理的灰鼠移入噪声室 ,在强度为 12 0dB、中心频率在 4kHz的脉冲噪声环境暴露 6小时 ;另外 6只经卡铂处理的灰鼠不经噪声暴露作为对照组。在噪声暴露后 30天取出耳蜗 ,常规制备耳蜗铺片 ,然后进行全耳蜗毛细胞计数 ,并将各组动物的毛细胞计数结果制备成平均受损情况分布图 ,观察和比较噪声引起的外毛细胞损害水平在具有正常内毛细胞的灰鼠和丧失内毛细胞的灰鼠是否存在差别。结果　单纯注射卡铂的灰鼠内毛细胞平均损失在 90 %左右 ,但外毛细胞无损害。经噪声暴露的正常灰鼠外毛细胞在耳蜗底回中部约相当于 4kHz共振频率区域平均损失 6 0 % ,但是在该区域两侧靠近底回和顶回的外毛细胞损失少于 2 0 %。预先经卡铂破坏 95 %内毛细胞的灰鼠经噪声暴露后 ,外毛细胞在耳蜗底回中部平均损失达到 90 % ,在该区域两侧的外毛细胞损失百分比大于 4 0 %。结论　内毛细胞缺损可以造成更多的外毛细胞在噪声刺激中被破坏 ,提示正常内毛细胞的存在可能有     

大鼠单侧耳蜗损毁对耳蜗核中γ-氨基丁酸能神经元的影响

目的:研究大鼠单侧耳蜗损毁前后耳蜗核中γ-氨基丁酸(GABA)能阳性神经元的分布及数量。方法:应用免疫组织化学方法(SP法)行耳蜗核中GABA能阳性神经元分布的检测。结果:耳蜗核中GABA能神经元的体积较小、数量较多、着色很深。单侧耳蜗毁损后耳蜗核中GABA能阳性神经元的数量:术后1～2周术侧明显低于对侧(均P<0.01);术后3周上升,但仍低于对侧(P<0.05);术后1个月,术侧略低于对侧,但差异无统计学意义(P>0.05)。结论:单侧耳蜗损毁前后,GABA能阳性神经元的分布及数量在耳蜗核中呈一明显的动态变化过程,说明GABA能神经元参与了耳蜗毁损后初级听觉中枢的可塑性变化或功能重组的过程,提示GABA能神经元数量的增减可能为初级听觉中枢的重组所必需。     

听觉剥夺和耳蜗内电刺激引起幼鼠听觉通路bdnf和c-fos基因及蛋白改变

目的 观察耳聋幼鼠及耳聋后单耳植入电极电刺激后,其听皮层和下丘、耳蜗核三个部位的脑源性神经营养因子(brain-derived neurotrophic factor, bdnf)、c-fos基因、蛋白表达水平的变化情况。方法 将66只SD幼鼠随机分为6组,每组11只,分别为注射药物后耳聋4周组(A1组)及对照组(A2组),耳聋6周组(B1组)和及对照组(B2组),注射药物后3周接受耳蜗内电刺激组(C组),5周接受耳蜗内电刺激组(刺激时间为1周,D组)。于幼鼠颈背部、两侧下腹部皮下注射庆大霉素(总量为350mg/kg),0.5h后于相同部位注射呋塞米(总量为200mg/kg)。分别于注射药物后不同时间取听皮层、下丘及耳蜗核三个部位的组织行实时荧光定量PCR及免疫组织化学方法,观察bdnf及c-fos基因及蛋白表达的变化。结果 A1组在听皮层、下丘及耳蜗核部位的bdnf及c-fos基因及蛋白表达均较A2组上升,较C组下降(P＜0.05)。B1组在听皮层、下丘及耳蜗核部位bdnf及c-fos基因及蛋白表达均较B2组和D组下降(P＜0.05)。各组之间的差异均有统计学意义。结论 听觉剥夺可导致幼鼠听皮层、下丘和耳蜗核部位的bdnf及c-fos基因及蛋白早期表达增多,而晚期表达下降。耳蜗植入电极电刺激可导致幼鼠听皮层、下丘和耳蜗核部位的bdnf及c fos基因及蛋白表达增多。bdnf及c-fos基因及蛋白表达的动态变化反映三个部位的可塑性变化。     

定量观察卡铂引起的灰鼠耳蜗毛细胞和神经纤维的早期损害过程

目的：定量观察和比较灰鼠耳蜗毛细胞和缰孔内神经纤维数量在卡铂耳中毒早期损害过程中的变化。方法：在耳蜗基底膜铺片的基础上制备耳蜗毛细胞图；从骨性螺旋板切片上对缰孔内的神经纤维计数。结果：缰孔内的神经纤维数量在注射卡铂后24h内明显减少。而内毛细胞的缺失是发生在注射上学铂后72h。结论：在卡铂耳中毒早期，缰孔内神经纤维的破坏早于内毛细胞的缺失。     

Auditory plasticity and hyperactivity following cochlear damage

This paper will review some of the functional changes that occur in the central auditory pathway after the cochlea is damaged by acoustic overstimulation or by carboplatin, an ototoxic drug that selectively destroys inner hair cells (IHCs) in the chinchilla. Acoustic trauma typically impairs the sensitivity and tuning of auditory nerve fibers and reduces the neural output of the cochlea. Surprisingly, our results show that restricted cochlear damage enhances neural activity in the central auditory pathway. Despite a reduction in the auditory-nerve compound action potential (CAP), the local field potential from the inferior colliculus (IC) increases at a faster than normal rate and its maximum amplitude is enhanced at frequencies below the region of hearing loss. To determine if this enhancement was due to loss of sideband inhibition, we recorded from single neurons in the IC and dorsal cochlear nucleus before and after presenting a traumatizing above the unit's characteristic frequency (CF). Following the exposure, some neurons showed substantial broadening of tuning below CF, less inhibition, and a significant increase in discharge rate, consistent with a model involving loss of sideband inhibition. The central auditory system of the chinchilla can be deprived of some of its cochlear inputs by selectively destroying IHCs with carboplatin. Selective IHC loss reduces the amplitude of the CAP without affecting the threshold and tuning of the remaining auditory nerve fibers. Although the output of the cochlea is reduced in proportion to the amount of IHC loss, the IC response shows only a modest amplitude reduction, and remarkably, the response of the auditory cortex is enhanced. These results suggest that the gain of the central auditory pathway can be up- or down regulated to compensate for the amount of neural activity from the cochlea.     

OTOTOXIC EFFECTS OF CARBOPLATIN IN ORGANOTYPIC CULTURES IN CHINCHILLAS AND RATS

Carboplatin, a second-generation platinum chemotherapeutic drug, is considerably less ototoxic than cisplatin. While common laboratory species such as mice, guinea pigs and rats are highly resistant to carboplatin ototoxicity, the chinchilla stands out as highly susceptible. Moreover, carboplatin causes an unusual gradient of cell death in chinchillas. Moderate doses selectively damage type I spiral ganglion neurons (SGN) and inner hair cells (IHC) and the lesion tends to be relatively uniform along the length of the cochlea. Higher doses eventually damage outer hair cells (OHC), but the lesion follows the traditional gradient in which damage is more severe in the base than the apex. While carboplatin ototoxicity has been well documented in adult animals in vivo, little is known about its in vitro toxicity. To elucidate the ototoxic effects of carboplatin in vitro, we prepared cochlear and vestibular organotypic cultures from postnatal day 3 rats and adult chinchillas. Chinchilla cochlear and vestibular cultures were treated with carboplatin concentrations ranging from 50 μM to 10 mM for 48 h. Consistent with in vivo data, carboplatin selectively damaged IHC at low concentrations (50-100 μM). Surprisingly, IHC loss decreased at higher doses and IHC were intact at doses exceeding 500 μM. The mechanisms underlying this nonlinear response are unclear but could be related to a decrease in carboplatin uptake via active transport mechanisms (e.g., copper). Unlike the cochlea, the carboplatin dose-response function increased with dose with the highest dose destroying all chinchilla vestibular hair cells. Cochlear hair cells and auditory nerve fibers in rat cochlear organotypic cultures were unaffected by carboplatin concentrations <10 μM; however, the damage in OHC were more severe than IHC once the dose reached 100 μM. A dose at 500 μM destroyed all the cochlear hair cells, but hair cell loss decreased at high concentrations and nearly all the cochlear hair cells were present at the highest dose, 5 mM. Unlike the nonlinear dose-response seen with cochlear hair cells, rat auditory nerve fiber and spiral ganglion losses increased with doses above 50 μM with the highest dose destroying virtually all SGN. The remarkable species differences seen in vitro suggest that chinchilla IHC and type I SGN posse some unique biological mechanism that makes them especially vulnerable to carboplatin toxicity.     

Carboplatin-induced early cochlear lesion in chinchillas

Carboplatin preferentially damages inner hair cells (IHC) and type I spiral ganglion neurons (SGNs) in the chinchilla; however, the temporal sequence of events leading to the destruction of these structures is poorly understood. To better understand the mechanisms leading up to the destruction of IHCs and type I SGNs, we measured the activity in single auditory nerve fibers for the first 8 h following carboplatin treatment and also monitored the development of histopathologies in SGNs and IHCs using a dose of carboplatin that killed approximately 50% of the IHCs. The spontaneous discharge rate (SDR) showed a slight increase around 3 h post carboplatin followed by a significant decline at 4-5 h. The saturation driven discharge rate (DDR) showed a significant increase 1-5 h post carboplatin. These physiological changes were associated with the formation of small vacuoles in type I afferent terminals and proximal nerve fibers 1-6 h post carboplatin; signs of IHC damage were first observed around 24-48 h. Thus, the neurotoxic effects of carboplatin occur approximately a day before the IHCs are damaged. The large fluctuations in SDR and DDR that occur several hours after carboplatin treatment are most likely due to the neurotoxic effects of carboplatin.     

D-Methionine attenuates inner hair cell loss in carboplatin-treated chinchillas

Carboplatin, a second-generation platinum-based antineoplastic drug, preferentially destroys inner hair cells (IHCs) in the chinchilla while sparing outer hair cells (OHCs). D-Methionine (D-Met), a sulfur-containing amino acid, has been shown to protect hair cells from cisplatin damage in rats, but its ability to protect IHCs from carboplatin damage has not yet been evaluated in the chinchilla. We tested whether D-Met would protect the hair cells in the chinchilla from carboplatin. Animals were divided into two groups: a control group that only received carboplatin (100 mg/kg, i.p.) and an experimental group that received 300 mg/kg D-Met (i.p.) 30 min before carboplatin treatment. Ototoxicity was assessed by measuring the amount of IHC and OHC loss. Average IHC loss in the group treated with D-Met was 62% compared with 84% in the untreated control group. Thus, D-Met causes a statistically significant reduction in IHC loss induced by carboplatin.     

Calpain Immunoreactivity and Morphological Damage in Chinchilla Inner Ears after Carboplatin

Carboplatin produces an unusual pattern of damage in the chinchilla inner ear, characterized by early destruction of type I afferent fibers and preferential loss of type I hair cells in the vestibular end organs and inner hair cells (IHCs) in the cochlea. In the present study, we investigated a potential role of calpains, a family of calcium-activated proteases, in carboplatin ototoxicity. Chinchillas received carboplatin (100 mg/kg IP) and were sacrificed 12, 24, 48, or 72 h later for morphological evaluation or immunocytochemistry. Nerve fibers and myelin were the initial sites of increased calpain immunoreactivity (IR) and morphological damage. At 12 h, granular immunoreactive puncta were present within nerve fibers and their myelin sheaths in the spiral ganglion. In the habenula perforata, dense reaction product was present in large vacuoles in the myelin surrounding the nerve fibers. At 24 h, nerve fibers and myelin were destroyed in the habenula, and those in the spiral ganglion showed increased calpain IR and morphological damage. At 72 h, nerve fibers and myelin were completely destroyed. Calpain IR was not a prominent feature of IHCs, type I vestibular hair cells, or ganglion cells at any time after carboplatin. The results show a correlation between calpain IR and carboplatin-induced axon and myelin degeneration. We propose that calpain-induced axonopathy and myelinopathy are primary features of carboplatin ototoxicity in chinchilla.     

Strategies to preserve or regenerate spiral ganglion neurons

PURPOSE OF REVIEW: Degeneration of spiral ganglion neurons following hair cell loss carries critical implications for efforts to rehabilitate severe cases of hearing loss with cochlear implants or hair cell regeneration. This review considers recently identified neurotrophic factors and therapeutic strategies which promote spiral ganglion neuron survival and neurite growth. Replacement of these factors may help preserve or regenerate the auditory nerve in patients with extensive hair cell loss. RECENT FINDINGS: Spiral ganglion neurons depend on neurotrophic factors supplied by hair cells and other targets for their development and continued survival. Loss of this trophic support leads to spiral ganglion neuron death via apoptosis. Hair cells support spiral ganglion neuron survival by producing several peptide neurotrophic factors such as neurotrophin-3 and glial derived neurotrophic factor. In addition, neurotransmitter release from the hair cells drives membrane electrical activity in spiral ganglion neurons which also supports their survival. In animal models, replacement of peptide neurotrophic factors or electrical stimulation with an implanted electrode attenuates spiral ganglion neuron degeneration following deafferentation. Cell death inhibitors can also preserve spiral ganglion neuron populations. Preliminary studies show that transfer of stem cells or neurons from other ganglia are two potential strategies to replace lost spiral ganglion neurons. Inducing the regrowth of spiral ganglion neuron peripheral processes to approximate or contact cochlear implant electrodes may help optimize signaling from a diminished population of neurons. SUMMARY: Recent studies of spiral ganglion neuron development and survival have identified several trophic and neuritogenic factors which protect these specialized cells from degeneration following hair cell loss. While still preliminary, such strategies show promise for future clinical applications.     

Pattern of hair cell loss and delayed peripheral neuron degeneration in inner ear by a high-dose intratympanic gentamicin

To gain insights into the ototoxic effects of aminoglycoside antibiotics (AmAn) and delayed peripheral ganglion neuron death in the inner ear, experimental animal models were widely used with several different approaches including AmAn systemic injections, combination treatment of AmAn and diuretics, or local application of AmAn. In these approaches, systemic AmAn treatment alone usually causes incomplete damage to hair cells in the inner ear. Co-administration of diuretic and AmAn can completely destroy the cochlear hair cells, but it is impossible to damage the vestibular system. Only the approach of AmAn local application can selectively eliminate most sensory hair cells in the inner ear. Therefore, AmAn local application is more suitable for studies for complete hair cell destructions in cochlear and vestibular system and the following delayed peripheral ganglion neuron death. In current studies, guinea pigs were unilaterally treated with a high concentration of gentamicin (GM, 40 mg/ml) through the tympanic membrane into the middle ear cavity. Auditory functions and vestibular functions were measured before and after GM treatment. The loss of hair cells and delayed degeneration of ganglion neurons in both cochlear and vestibular system were quantified 30 days or 60 days after treatment. The results showed that both auditory and vestibular functions were completely abolished after GM treatment. The sensory hair cells were totally missing in the cochlea, and severely destroyed in vestibular end-organs. The delayed spiral ganglion neuron death 60 days after the deafening procedure was over 50%. However, no obvious pathological changes were observed in vestibular ganglion neurons 60 days post-treatment. These results indicated that a high concentration of gentamycin delivered to the middle ear cavity can destroy most sensory hair cells in the inner ear that subsequently causes the delayed spiral ganglion neuron degeneration. This model might be useful for studies of hair cell regenerations, delayed degeneration of peripheral auditory neurons, and/or vestibular compensation. In addition, a potential problem of ABR recording for unilateral deafness and issues about vestibular compensation are also discussed.     

对灰鼠延迟性神经元死亡模型中螺旋神经节细胞缺损的评估

目的探索观察耳蜗螺旋神经节细胞的简便定量研究方法 ,并在灰鼠延迟性螺旋神经节细胞死亡动物模型中验证本方法的实用性和可靠性。方法 15只成年灰鼠平均分为3组,第1组用于正常对照;第2组一次性同时肌肉注射庆大霉素（125mg/kg）和静脉注射利尿酸钠（40mg/kg）,并在用药后2个月处死;第3组接受与第2组同样的药物注射,但在用药后4个月处死。耳蜗样品被常规应用环氧树脂包埋并制作成耳蜗中轴半薄切片,计数耳蜗各回蜗轴螺旋管腔切片截面内的螺旋神经节数量并进行统计分析。结果灰鼠耳蜗底回起始端的蜗轴螺旋管腔比耳蜗底回中部和耳蜗中回大,因此耳蜗底回起始端蜗轴螺旋管内的螺旋神经节细胞数量多于耳蜗底回中部和耳蜗中回。耳蜗毛细胞被彻底破坏后2个月,与正常灰鼠耳蜗各回蜗轴螺旋管腔切片截面内的螺旋神经节细胞数量相比,耳蜗底回蜗轴螺旋管切片截面内的螺旋神经节细胞减少数量比耳蜗中回严重,提示延迟性螺旋神经节细胞死亡可能遵循着从耳蜗底回向顶回扩展的规律。耳蜗毛细胞被彻底破坏后4个月,全耳蜗蜗轴螺旋管内的螺旋神经节细胞基本上丧失殆尽。结论计数耳蜗中轴切片各回蜗轴螺旋管腔切片截面内的螺旋神经节细胞数量是一种简便可靠的定量分析方法 。     

Spiral ganglion loss outpaces inner hair cell loss in endolymphatic hydrops

Objectives/Hypothesis:

Neuronal toxicity is thought to be important in Meniere's disease and experimental endolymphatic hydrops (ELH). This study quantifies the relationship between neuronal degeneration and hair cell degeneration in ELH to evaluate the hypothesis that a primary neural insult would yield greater loss in the spiral ganglion than at the inner hair cell level.

Study Design:

Following induction and histopathologic confirmation of endolymphatic hydrops in guinea pigs, the degree of hydrops, spiral ganglion loss, and hair cell degeneration were quantified and compared.

Methods:

Guinea pigs with surgically induced unilateral hydrops were sacrificed and their cochleas preserved. Hydrops severity and spiral ganglion density were quantified using automated methods. Hair cells were counted manually. Values were normalized against the contralateral ear to create loss indexes.

Results:

Inner hair cell (IHC) loss at the apex is significantly lower than corresponding neuronal loss. IHC loss at the base is also lower than neuron loss, although not significantly. Regression analysis shows a significant, positive correlation between neuron loss severity and IHC loss severity at the apex, but not at the base. There is no correlation between hydrops severity and inner hair cell loss.

Conclusions:

By confirming that spiral ganglion loss is more severe than hair cell loss, and that hair cell loss appears to worsen with neuronal degeneration, this study supports the theory that neuronal toxicity is the primary insult in ELH‐related disorders, such as Meniere's disease, and may provide the basis for designing treatment strategies. Laryngoscope, 2010