经圆窗应用地塞米松对豚鼠庆大霉素耳毒性的拮抗作用北大核心CSCD

目的探讨经圆窗局部应用地塞米松和全身应用地塞米松对庆大霉素致聋豚鼠耳蜗损害的拮抗作用。方法选用听力正常豚鼠60只,随机分为4组:①庆大霉素组,肌肉注射庆大霉素120mg·kg-1·d-1,1次/天,共10天;②全身用药组,肌肉注射庆大霉素(用法同庆大霉素组),同时腹腔注射地塞米松2.5mg·kg-1·d-1,1次/天,共10天;③局部用药组,肌肉注射庆大霉素(用法同庆大霉素组),右耳经圆窗局部用明胶海绵浸地塞米松(5mg/ml)约0.1ml,共1次。④对照组:肌肉注射与庆大霉素等体积的生理盐水,1次/天,共10天,右耳经圆窗局部用地塞米松1次。于实验前、停药后第1天和第10天分别检测各组动物的听性脑干反应(ABR),显微镜下观察中耳粘膜反应,扫描电镜观察耳蜗毛细胞的形态学变化。结果停药第10天,除对照组外,庆大霉素组、全身用药组、局部用药组动物ABR反应阈较实验前均有不同程度的升高,其中庆大霉素组的反应阈明显高于局部用药组(P<0.05)。扫描电镜下可见庆大霉素组动物耳蜗毛细胞损害严重,而全身和局部用药组动物耳蜗毛细胞损伤程度明显减轻;各组动物中耳粘膜正常。结论地塞米松可以在一定程度上减轻庆大霉素所致的耳毒性,经圆窗局部给药的效果优于全身应用。     

银杏叶提取物对顺铂耳蜗毒性的拮抗作用

目的 研究银杏叶提取物对顺铂耳毒性的拮抗作用。方法 杂色健康豚鼠27只，随机分为生理盐水组、顺铂（CDDP）组、银杏叶提取物（Egb CDDP）组，动态观察动物听阈变化及耳蜗外毛细胞形态学改变，并在损伤6天后，观察外毛细胞损伤率、耳蜗毛细胞凋亡情况。结果 CDDP组听阈及外毛细胞损伤率显著性升高，凋亡现象明显；Egb CDDP组外毛细胞的损伤率及听阈损伤均明显减轻，仅出现早期凋亡表现；生理盐水组各项指标均无明显变化。结论 Egb对顺铂所致的耳毒性具有明显拮抗作用。     

脑活素拮抗豚鼠庆大霉素耳毒性机理的研究

目的探讨脑活素拮抗豚鼠庆大霉素耳毒性作用机理。方法取听力正常豚鼠60只,随机分为4组,每组15只A组(脑活素组),肌肉注射脑活素360mg·kg-1·d-1;B组(庆大霉素组),肌肉注射庆大霉素120mg·kg-1·d-1;C组(庆大霉素 脑活素组),肌肉注射庆大霉素 脑活素,剂量同上;D组(生理盐水组),肌肉注射等量生理盐水。各组均连续用药10d再饲养一周,第17d处死,取左侧听泡,进行琥珀酸脱氢酶化学组织染色观察其活性;取右侧听泡行石蜡包埋切片,在光镜下进行螺旋神经节细胞计数,免疫组织化学SP法检测脑源性神经生长因子(brain-derivedneurotrophicfactor,BDNF)在耳蜗中的表达。结果庆大霉素 脑活素组螺旋神经节细胞退行性病变数目明显低于庆大霉素组,神经纤维变性明显较少,琥珀酸脱氢酶活性明显增高,BDNF在耳蜗中呈阳性表达。结论脑活素对庆大霉素所致耳毒性有明显保护作用,其机理在于脑活素能拮抗庆大霉素对毛细胞有氧代谢的抑制,与BDNF对螺旋神经元的营养修复作用有关。     

一氧化氮对庆大霉素耳毒性的影响

目的研究耳蜗内不同水平的一氧化氮(NO)含量对庆大霉素(GM)耳毒性的影响.方法将实验动物豚鼠随机分为GM组;庆大霉素加左旋精氨酸(GM加L-Arg)组;庆大霉素加NG-单甲基-L-精氨酸(GM加L-NMMA)组和正常对照组.实验过程中观察动物体重变化,检测ABR反应阈;取标本检测血清和耳蜗组织NO含量,耳蜗铺片观察毛细胞损失程度.结果对照组动物体重增加明显,各实验组体重增加缓慢,其中GM加L-Arg组体重略有下降.实验第4周,GM加L-Arg组ABR反应阈升高明显,与GM组比较有统计学意义(P<0.05),GM加L-NMMA组ABR反应阈升高较少,与GM组比较有统计学意义(P<0.05).GM加L-Arg组血清和耳蜗NO含量明显升高,GM加L-NMM A组NO含量升高不明显,与GM组比较差异具有显著性(P<0.05).耳蜗铺片各组毛细胞损失程度与ABR变化相对应.结论增加耳蜗NO含量可增加GM耳毒性,减少耳蜗NO含量可减轻GM耳毒性.     

聚天冬氨酸对庆大霉素抑制耳蜗肌醇脂质信使系统的影响

目的 观察聚天冬氨酸(polyaspartic acid,PAA)对庆大霉素(gentamicin,GM)抑制耳蜗肌醇脂质信使系统的影响,进一步探讨PAA对庆大霉素耳毒性拮抗作用机制。方法 采用[~3H]-肌醇参入法和高效液相色谱分析法(high performance liquid chromatography,HPLC)测定不同给药组、不同给药时间豚鼠耳蜗组织肌醇磷酸酯(inositolphosphates,IPs)、多磷酸肌醇磷脂(polyphosphatidylinositol,PPI)及磷脂酶 C(PPI phospholipase C,PLC)。结果 ①给药1天后不同给药组间耳蜗组织IPs、PPI及PLC均无显著性差异(P>0.05)。②给药5天后单用GM组耳蜗组织PPI增加、Ips和PLC减低,与PAA+GM组及其他二对照组间有显著性差异(P<0.01)。③给药10天后单用GM组耳蜗组织PPI、IPs及PLC与PAA+GM组及其他二对照组间有显著性差异(P<0.01),但与单用GM5天相比,PPI变化不明显,IPs和PLC升高。结论 PAA对GM抑制耳蜗肌醇磷酸酯信使系统有拮抗作用,从而起到对GM耳毒性连锁反应早期阶段的保护作用。     

丹参注射液对豚鼠耳蜗毛细胞的影响

目的观察丹参注射液对豚鼠庆大霉素耳中毒引起的耳蜗毛细胞酸性磷酸酶变化的影响。方法选用耳廓反射正常,体重250g～300g的健康杂色豚鼠,雌雄不限,随机分成3组,正常对照组15只,肌肉注射生理盐水2ml/(kg·d);庆大霉素组15只,肌肉注射庆大霉寨80mg／(kg·d);丹参注射液组15只,腹腔注射丹参注射液6mg／(kg·d),然后肌肉注射庆大霉素同庆大霉素组。各组动物连续注射药物均20天。用脑干听觉诱发电位(auditory brainstem response audiometry,ABR)检查豚鼠的听阈变化情况;用组织化学方法检测耳蜗毛细胞酸性磷酸酶的变化情况。结果正常对照组、庆大霉素组和丹参注射液组动物的ABR阈值分别为：(34.50±1.22)dB peSPL、(34.25±1.18)dBpeSPL和(34.39±1.27)dB peSPL;用药后第22天,反应阈值分别为：(34.65±1.32)dB peSPL、(71.25±24.73)dB peSPL和(41.05±10.93)dB peSPL。对照组分别与庆大霉素、丹参注射液组比较,差异显著(t=8.097,3.184,P＜0.01);丹参注射液组与庆大霉察组比较,有显著性差异(t=6.118,P＞0.01)。耳蜗铺片光镜下观察毛细胞酸性磷酸酶染色：正常对照组呈棕褐色,显色分布均匀,毛细胞排列整齐;庆大霉素组毛细胞依动物耳聋程度不同而出现不同程度染色缺失,庆大霉素组染色缺失显著,丹参注射液组染色缺失轻,两组比较有明显差异。结论丹参注射液能明显降低庆大霉素的耳毒性;保护耳蜗毛细胞溶酶体的完整性,降低庆大霉素对溶酶体的损坏而造成的毛细胞自溶性损伤,是丹参注射液降低庆大霉索耳毒性的机制之一。     

川芎嗪对庆大霉素耳中毒耳蜗外毛细胞和血管纹的保护作用

目的：探讨在庆大霉素（gentamycin，GM）耳中毒情况下，川芎嗪（tetramethylpyrazine，TMP）对豚鼠耳蜗外毛细胞和血管纹边缘细胞的保护作用。方法：12只豚鼠随机分为GM组、联合用药组、TMP组及对照组，用药十天后处死，采用透射电镜观察耳蜗外毛细胞及血管纹边缘细胞超微结构，扫描电镜观察血管纹边缘细胞表面形态。结果：透射和扫描电镜显示，联合用药组外毛细胞及血管纹边缘细胞超微及表面结构破坏不均明显轻于庆大霉素组，特别是其中的线粒体结构破坏与数目减少更显著轻于庆大霉素组。结论：川芎嗪具有保护庆大霉素耳中毒耳蜗外毛细胞和血管纹结构的作用，从而拮抗庆大霉素耳毒性。     

白藜芦醇拮抗庆大霉素耳毒性的实验研究

目的观察白黎芦醇（resveratrol,Res）对抗庆大霉素耳毒性的作用.方法将豚鼠随机分为庆大霉素（gentamicin, GM）组、白藜芦醇剂量I＋GM组 （ResI ）、白黎芦醇剂量II＋GM组（ResII）、白黎芦醇剂量III＋GM组（ResIII）及对照组.采用听性脑干反应（ABR）、耳蜗铺片及透射电镜技术,观察用药前后各组动物听阈及耳蜗毛细胞形态学改变,并检测血清丙二醛、超氧化物岐化酶含量、肾功能以及庆大霉素血药浓度.结果 ResIII组血液中丙二醛较GM组明显减少（P〈0.05）,GM＋Res各组超氧化物歧化酶活性均明显高于GM组（P〈0.05）,同时GM组1、8 kHz ABR 4 周平均阈移与ResIII剂量组间差异显著（P〈0.05）.形态学改变与听力变化一致.Res对庆大霉素血药浓度没有影响.结论大剂量Res能有效减轻GM的耳毒性作用,且不影响庆大霉素的抗菌作用.     

灯盏花素对顺铂所致豚鼠耳蜗损伤的拮抗作用

目的探讨灯盏花素对顺铂致豚鼠耳毒性的拮抗作用。方法将30只豚鼠分为三组:正常对照组(A组)、实验对照组(B组)、实验组(C组),每组10只。B组和C组一次性腹腔注顺铂10 mg/kg,同时C组连续10天腹腔注射灯盏花素15 mg.kg-1.d-1,B组等时程腹腔注等量生理盐水。每组豚鼠在实验前后均行听性脑干反应(ABR)检测。在豚鼠顺铂致耳毒性模型完成并检测ABR反应阈后,用免疫组织化学方法检测4-羟基-2-壬烯醛(4-HNE)在各组动物耳蜗的表达,同时用扫描电镜观察各组豚鼠耳蜗形态。结果实验前三组豚鼠ABR反应阈差异无统计学意义(P>0.05),实验后B组和C组豚鼠ABR反应阈分别为50.12±18.45、36.32±15.63 dB SPL,均明显高于实验前,且B组显著高于C组(P<0.05),B组豚鼠听功能损伤明显重于C组。4-HNE在A组表达呈阴性,在B组和C组耳蜗表达呈阳性,且在B组的表达明显强于C组。B组耳蜗外毛细胞的损伤明显较C组重。结论 4-HNE在顺铂所致豚鼠耳蜗损伤中呈阳性表达。灯盏花素对4-HNE的形成有明显抑制作用,且能拮抗顺铂对豚鼠的耳蜗毒性,表明活性氧(ROS)在顺铂所致豚鼠耳蜗损伤中起重要作用。     

α—硫辛酸对庆大霉素所致大鼠耳毒性损害的保护作用

目的 探讨高效抗氧剂α-硫辛酸是否对庆大霉素所致的大鼠耳蜗毒性有防护作用.方法 将30只Wistar大鼠随机分成庆大霉素(GM)组、α-硫辛酸(α-LA)+庆大霉素(GM)组及正常对照组,GM组每日腹腔注射GM100mg/kg;GM+α-LA组每日同时腹腔注射GM100mg/kg和α-LA注射液10mg/kg;正常对照组每日腹腔注射生理盐水100mg/kg.3组皆连续用药10d,用药前后测试DPOAE.最后将动物处死,取听泡,观察毛细胞形态.实验数据进行统计学分析.结果 DPOAE停药后,GM+α-LA组DPOAE幅值有轻度降低;GM组DPOAE幅值明显降低; 2组用药前后比较有显著性差异(P<0.01).GM+α-LA组大鼠听功能受损程度明显轻于GM组.正常对照组大鼠用药前后DPOAE幅值及形态学无明显变化.形态学观察:给药后GM组耳蜗底回外毛细胞均有较重损伤,前庭毛细胞空泡样改变,纤毛倒伏缺失明显.GM+α-LA组耳蜗底回外毛细胞损伤明显减轻,前庭毛细胞散在缺失.正常对照组耳蜗底回外毛细胞和前庭毛细胞基本正常.结论 在使用GM的同时联合应用α-LA可有效减少GM对大鼠的内耳毒性.     

Delayed nerve repair is associated with diminished neuroenhancement by FK506

OBJECTIVES/HYPOTHESIS: The immunosuppressive agent FK506 has been shown in many studies to enhance nerve regeneration and to accelerate functional recovery after immediate nerve repair. However, in clinical practice the diagnosis and treatment of patients with peripheral nerve injuries is often delayed. The study investigated whether FK506 would retain its neuroregenerative properties when nerve repair and initiation of FK506 therapy were delayed for 7 days. STUDY DESIGN: In vivo laboratory study. METHODS: Thirty-two Lewis rats underwent tibial nerve transection and were randomly assigned to four experimental groups: immediate repair with FK506 treatment, immediate repair without FK506 treatment, 7-day delayed repair with FK506 treatment, and 7-day delayed repair without FK506 treatment. Treated animals received daily subcutaneous injections of 2 mg/kg FK506. Serial walking track measurements were performed at 14, 16, and 18 days after nerve repair. On day 18 after repair, peripheral nerves were injected with a fluorescent tracer for retrograde labeling. On day 21, peripheral nerves and spinal cords were harvested for histomorphometric analysis and motor neuron cell body counts, respectively. RESULTS: Animals that underwent immediate repair with FK506 had significantly higher fiber counts and percentages of nerve than the other three groups (P <.05) but did not show statistically significant earlier functional recovery. The remaining three groups had intermediate levels of nerve regeneration that were not significantly different. Retrograde abled motor neurons counts were decreased in animals with delayed nerve repair that received no FK506 (P <.05). CONCLUSION: In a rat tibial nerve transection model, the neuroregenerative effects of FK506 diminished markedly when repair and initiation of FK506 therapy were delayed by 7 days.     

灯盏花对庆大霉素内耳毒性的防护作用

目的　探讨灯盏花对庆大霉素耳毒性的防护作用。方法　选用听力正常豚鼠 4 0只 ,随机分为 2组 :非治疗组 (庆大霉素组 ) ;治疗组 (庆大毒素 +灯盏花组 )。两组皆肌肉注射庆大霉素注射液 (12 0mg·kg-1·d-1) ,治疗组同时腹腔注射灯盏细辛注射液 (4 5mg·kg-1·d-1)连续 10天。分别于停药后第 1、7、14、2 1天随机抽取一定数量的豚鼠处死行毛细胞及血管纹的电镜及光镜观察 ,于处死前行畸变产物耳声发射 (DPOAE)、听性脑干反应 (ABR)检测。结果　非治疗组耳蜗功能和结构损害严重 ,外毛细胞的外形及核已固缩 ,血管纹毛细血管数量随用药后时间的延长逐渐稀少、管径狭窄。治疗组耳蜗功能和结构损伤较轻 ,除可见轻度胞质水肿及线粒体固缩外 ,外毛细胞基本正常 ,血管纹毛细血管管径有所增宽 ,DPOAE振幅和ABR波潜伏期、阈值两组比较有显著性差异 (P <0 .0 1)。结论　灯盏花对庆大霉素耳毒性有一定的防护作用     

Effect of FK506 on apoptosis of facial motor neurons in rats and its possible mechanism

To investigate the effect of FK506 on apoptosis of facial motor neurons in rats and its possible mechanism. A total of 48 Wistar rats were randomly divided into experimental group and control group. Facial nerve injury model was established by transection of facial nerve at stylomastoid foramen. Rats in experimental group and control group were provided with FK506 and normal saline by intraperitoneal injection, respectively. The morphology of facial neurons was observed under light microscope at different time points after injury. Apoptotic facial motor neurons were detected by TdT-mediated dUTP-biotin nick and labeling (TUNEL) staining, and expression of bcl-2 and bax was evaluated by immunohistochemistry. After facial nerve transection, the apoptotic cells in experimental group significantly decreased compared to control group (P < 0.05), with higher expression of bcl-2 and lower expression of bax in experimental group. FK506 could inhibit apoptosis of facial motor neurons after facial nerve transection, possibly via up-regulation of bcl-2 expression and down-regulation of bax expression.     

中国耳鼻咽喉颅底外科杂志作者稿件学术不端常见问题分析

目的观察针刺内听宫穴对庆大霉素致聋大鼠听力的改善作用。方法20只成年大鼠平均分为4组,庆大霉素组每日上午腹腔注射庆大霉素100mg／kg,连续14d;内听宫组庆大霉素给药方法同庆大霉素组,自腹腔注射庆大霉素第1天开始,隔日下午进行针刺内听宫穴,共10次;听宫组庆大霉素给药方法同庆大霉素组,自腹腔注射庆大霉素第1天开始,隔日下午进行针刺听宫穴,共10次;对照组每日上午腹腔注射等剂量生理盐水,共10次。分析实验前、实验14d及20d各组大鼠听性脑干反应阈,评价各组大鼠听力情况。结果庆大霉素组的听性脑干反应阈明显高于内听宫组、听宫组及对照组,内听宫组与听宫组听性脑干反应阈比较无明显差异。结论针刺内听宫穴及听宫穴均可在一定程度上降低庆大霉素致聋大鼠听性脑干反应阈,减轻庆大霉素耳毒性,缓解药物对听力的损害作用,是治疗药物性耳聋的有效穴位。     

Intracochlear infusion of buthionine sulfoximine potentiates carboplatin ototoxicity in the chinchilla

The aim of this experiment was to determine if buthionine sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, enhances the ototoxicity of carboplatin. Osmotic pumps were used to infuse BSO into the right cochleas of 12 adult chinchillas for 14 days. The left cochleas served as controls. Animals were assigned to three groups: a drug control group that did not receive carboplatin, a group that received a single dose of carboplatin (25 mg/kg i.p.), and a group that received a double dose of carboplatin (25 mg/kg i.p. x 2), with 4 days between injections. Carboplatin was administered after three days of BSO pre-treatment. Ototoxicity was assessed with evoked potentials recorded from electrodes implanted in the inferior colliculi (ICPs), distortion product otoacoustic emissions (DPOAEs), and cochleograms. BSO infusion itself caused no long-term functional or morphological changes. One of four animals treated with it single dose of carboplatin showed a significant loss of inner hair cells (IHCs), with greater loss in the BSO-treated ear. All animals in the double-dose carboplatin group showed marked differences between BSO-treated and control ears. Average IHC losses were 59% in BSO-treated ears vs. 18% in control ears. Moreover, BSO-treated ears sustained significantly greater outer hair cell (OHC) losses than control ears (37% vs. 2%, respectively). ICP and DPOAE response amplitudes were reduced slightly in BSO-treated ears relative to control ears, consistent with their greater hair cell loss. The results clearly show that BSO can enhance carboplatin ototoxicity in the chinchilla, supporting a role of GSH and reactive oxygen species in platinum ototoxicity.     

Effect of sodium thiosulfate on cisplatin-induced ototoxicity

The effect of sodium thiosulfate (STS) on cisplatin (CDDP)-induced ototoxicity in the guinea pigs was studied by surface preparation, outer hair cell counting, electrocochleographic, light and electron microscopic techniques. Seventy-eight guinea pigs were divided into five groups. Group I received intraperitoneal CDDP (2.5 mg/kg/day) alone: group V as control; the other three groups were given the same doses of CDDP as group I with intramuscular STS (600 mg/kg/day) administered 30 min before (group II) or 30 min (group III) and 6 hr (group IV) after CDDP. The results showed that CDDP produced serious ototoxicity both functionally and histologically when given without STS. The first row of outer hair cells (OHC) in basal turn was first damaged. The inner hair cells (IHC) were more resistant than the OHC. The pattern of destruction is similar to that produced by aminoglycosides. Concomitant use of STS, however, significantly reduced CDDP-induced ototoxicity. Transmission electron microscopy showed the degeneration of mitochondria to be the major and earliest sign of OHC damage induced by CDDP. Our present study documented the good protective efficacy of STS against CDDP cochleotoxicity. STS did not reverse the pathological changes already caused by CDDP. This study provided some experimental evidence for the prevention of CDDP ototoxicity in clinical cancer chemotherapy.     

Otologic effects of topical mitomycin C: phase I-evaluation of ototoxicity.

HYPOTHESIS: To determine ototoxicity of topical mitomycin C when placed in the middle ear at varying concentrations. BACKGROUND: Despite meticulous surgical technique and diligent postoperative care, some patients develop excessive scar and granulation tissue in the middle ear or mastoid cavity. Poor wound healing may result in infection, tympanic membrane perforation, or conductive hearing loss, which may necessitate further surgery. Use of topical mitomycin C in the ear may be beneficial in reducing scar and granulation tissue formation. This phase of the study was developed to determine the safety of topical mitomycin C in the rat model relative to ototoxicity. METHODS: Twelve Sprague-Dawley rats were evaluated with auditory brainstem response testing before and after treatments. Topical mitomycin C was injected in the middle ear of the right ear of eight animals. Varying concentrations of 0.125 to 0.5 mg/ml were used. Saline was injected in the left ear of each animal to serve as a control. Four separate animals were evaluated with placement of topical mitomycin C on Gelfoam into the middle ear. In two animals, Gelfoam was placed in the middle ear for 1 minute and then removed. In two animals, Gelfoam was placed in the middle ear and left in place. Auditory brainstem response testing was performed at 4 weeks and at 8 weeks. RESULTS: Using a high concentration of mitomycin C (>0.25 mg/ml) resulted in ototoxicity, with an increase in the auditory brainstem response threshold at 4 weeks and at 8 weeks. At low concentrations (<0.20 mg/ml), no change in auditory brainstem response threshold was noted. Animals treated with Gelfoam soaked in mitomycin C showed no change in auditory brainstem response threshold. CONCLUSION: The results of this study indicate that topical mitomycin C on Gelfoam applied in the middle ear appears safe when low concentrations are used, even in the rat, which has a higher susceptibility to gentamycin toxicity than humans. Higher concentrations may lead to ototoxicity based on changes in Wave V on auditory brainstem response. This treatment may prove to be an important option for patients suffering from chronic granulation tissue or scar tissue in the external or middle ear.     

Dose-dependent dual effect of melatonin on ototoxicity induced by amikacin in adult rats

Abtract The aim of this animal study was to reveal the dose-dependent effects of melatonin on aminoglycoside ototoxicity by utilizing distortion product otoacoustic emissions (DPOAEs). Forty-four adult (aged 12 months) rats were divided into five groups. Rats of the control group (group C) were injected with vehicle, while the melatonin group (group M) received melatonin (4 mg/kg per day); there were four rats in each of these groups. The study groups consisted of 12 rats per group, and they were treated as follows: 600 mg/kg per day amikacin (group A), amikacin plus a low dose (0.4 mg/kg per day) melatonin (group AML) and amikacin plus high dose (4 mg/kg per day) melatonin (group AMH) for 14 days. During the serial measurements on days 0, 5, 10 and 15, the DPOAE results of groups C,M and AML were not significantly changed. Amikacin ototoxicity findings for input/output (I/O) functions were detected on the 3rd measurement of the study in group A. High-dose melatonin clearly enhanced and accelerated amikacin-induced ototoxicity. The DP-gram amplitudes and I/O amplitudes were reduced, and I/O thresholds were increased in group AMH. Group AMH was the group that was affected the most and earliest by amikacin. Our study results showed that while low-dose melatonin protected the inner ear from ototoxicity, high dose melatonin facilitated amikacin-induced ototoxicity, possibly via the vasodilatory effect, leading to an increased accumulation of amikacin in the inner ear. Probably, the protective effect of the melatonin at a dose of 0.4 mg/kg per day is related to its antioxidant properties. Apparently, the vasodilatory effect of melatonin seems to be more prominent than its antioxidant effect in high doses.     

Effect of geranylgeranylacetone on gentamycin ototoxicity in rat cochlea culture

OBJECTIVE: Geranylgeranylacetone (GGA), an anti-ulcer drug, has been reported to induce heat shock proteins (HSPs) in several animal organs. Purpose of this study was to investigate whether GGA has protective effect on gentamycin (GM) ototoxicity and whether it induces HSP70 in rat cochlea. METHODS: We used cochlea explant culture from postnatal 5-day rat. Explants were pre-incubated with GGA, then incubated with GM and GGA. The number of surviving outer hair cells (OHCs) labeled by phalloidin was counted to evaluate the protective effect of GGA. The expression of HSP70 in whole cochlea tissue was investigated by immunoblot analysis. RESULTS: The number of surviving OHCs was significantly high in GGA 10(-5)M group compared to GM only group and GGA 10(-6)M group. In the immunoblot analysis, HSP70 levels in GGA added groups were slightly high compared to simple culture group, but much lower than those in heat shock group. CONCLUSION: It was suggested that GGA-induced HSP70, and had partial protective effects on GM ototoxicity in the cochlea. GGA has possibility to be safe and useful treatment drug for cochlea disorder.