c-fos及NR2A在耳鸣大鼠听皮层中的表达

目的通过检测神经元功能可塑性标记物快反应基因c-fos和N-甲基-D-天门冬氨酸受体（N-methyl-D-aspartate receptor,NMDAR）亚型NR2A在耳鸣大鼠听皮层中的表达探讨听皮层的可塑性变化及其在耳鸣产生中所起的作用.方法将30只白色Wistar大鼠随机分为3组,耳鸣模型组（12只）、生理盐水组（12只）和空白对照组（6只）.注射水杨酸钠造模并用行为学方法证实动物感受到耳鸣后,利用免疫组化技术检测动物听皮层中c-fos和NR2A的表达,并用数字图像分析系统进行分析.结果12只注射水杨酸钠的耳鸣模型组大鼠全部造模成功.c-fos基因的表达产物FOS蛋白主要存在于皮层神经元的胞核,其阳性细胞的数量及所占面积的百分比在耳鸣组显著高于对照组（P值均＜0.01）;NR2A受体主要表达在锥形细胞的胞膜上,其阳性细胞的数量、染色强度和面积百分比均显著强于对照组（P值均＜0.01）.结论耳鸣大鼠听皮层中c-fos和NR2A的表达明显增多,一方面表明神经递质及受体可能参与了耳鸣的发生;另一方面提示耳鸣大鼠听皮层中发生了功能可塑性改变,这种改变可能在耳鸣的发生发展中起重要作用.     

隔声后听觉重塑模型中听皮质突触NR2A表达的变化

目的：观察隔声后听觉重塑模型中听皮质突触N甲基-D-天冬氨酸（NMDA）受体亚基NR2A表达的变化。方法：采用清洁级SD大鼠45只,分成隔声组、隔声后听觉重塑组及对照组各15只,Optiprep沉降梯度超速离心从初级听皮质提取高度纯化的突触体后,采用Western blotting蛋白质印迹检测技术对生后隔声14d组、28d组、42d组、隔声7d后再给予纯音暴露的各实验组听皮质突触体NR2A表达进行比较。结果：隔声使生后14d组和28d组动物听皮层NR2A表达水平明显下降（P〈0．05）,隔声7d后再给予纯音暴露则又使NR2A表达水平明显提高（P〈0．05）,呈现双向调节趋势。隔声和纯音暴露对生后42d组成熟大鼠听皮层NR2A表达不再产生明显调节作用（P〉0．05）。结论：在大鼠生后发育关键期,听觉经验可改变听皮层NMDA受体NR2A蛋白表达水平。研究结果为研究感觉功能发育可塑性的机制提供了重要的实验资料。     

外周听觉改变致听皮质突触N-甲基D-天冬氨酸受体亚基表达变化

目的观察听觉剥夺后重塑模型中听皮质突触N-甲基D-天冬氨酸受体亚基(N-methyl-D-aspartate receptor subunit 2B,NR2B)表达变化。方法采用清洁级SD大鼠90只,分成听觉剥夺组、听觉剥夺后重塑组及对照组,Optiprep沉降梯度超速离心从初级听皮质提取高度纯化的突触体后,采用Western blotting蛋白质印迹检测技术对生后听觉剥夺14天组、28天组、42天组、听觉剥夺7天后再给予纯声暴露的各实验组听皮质突触体NR2B表达进行比较。结果听觉剥夺使生后14天组和28天组动物听皮层NR2B表达水平明显下降(P<0.05),听觉剥夺7天后再给予纯声暴露则又使NR2B表达水平明显提高(P<0.05),呈现双向调节趋势。听觉剥夺和纯声暴露对生后42天组成熟大鼠听皮层NR2B表达不再产生明显调节作用(P>0.05)。结论在大鼠生后发育关键期,听觉剥夺、可改变听皮层NMDA受体NR2B蛋白表达水平;为研究感觉功能发育可塑性机制提供了重要实验资料。     

耳鸣模型大鼠听皮层生长相关蛋白-43和细胞骨架活性调节蛋白的表达

目的检测神经元功能可塑性基因生长相关蛋白-43（growth associated protein,GAP-43）和细胞骨架活性调节蛋白（activity regulated cytoskeleton associated protein,ARC）在水杨酸诱导耳鸣大鼠听皮层中的表达,探讨其在耳鸣产生中的作用。方法将24只白色Wistar大鼠随机分为3组：水杨酸钠组（8只）、生理盐水组（8只）和空白对照组（8只）。前两组从条件反射建立前开始于每次条件反射训练前2小时分别腹腔注射10%水杨酸钠溶液（350mg/kg）和同体积生理盐水,至实验结束,空白对照组不做任何处理。通过行为学方法证实水杨酸钠组动物感受到耳鸣后,利用荧光定量PCR检测动物听皮层中GAP-43和ARC的表达。结果水杨酸钠组大鼠听皮层中GAP-43和ARC蛋白阳性神经元的表达（分别为2.17&#177;0.72、4.90&#177;2.13）明显高于生理盐水组（分别为1.05&#177;0.20、1.13&#177;0.42）和空白对照组（分别为0.96&#177;0.97、1.07&#177;0.70）（P〈0.01）,而生理盐水组和空白对照比较差异无统计学意义（P〉0.05）。结论耳鸣大鼠听皮层中神经元功能可塑性基因GAP-43和ARC蛋白阳性神经元的表达增加,推测它们可能在耳鸣的发生发展中起重要作用。     

耳鸣大鼠耳蜗核5-HTR1B/2C、GABA、GluR1/2表达的研究

目的通过检测耳鸣大鼠耳蜗核5-羟色胺受体1B(5-hydroxytryptamine receptor1B)和5-羟色胺受体2C(5-hydroxytryptamine receptor2C)、γ-氨基丁酸(γ-aminobutyricacid,GABA)、谷氨酸受体1(glutamate receptor1,GluR1))和谷氨酸受体2(glutamate receptor2,GluR2)表达情况,探讨其在耳鸣产生中所起的作用。方法将24只白色Wistar大鼠随机分为3组:Ⅰ组:空白对照组(8只)、Ⅱ组:生理盐水组(8只)和Ⅲ组:耳鸣模型组(8只)。将耳鸣模型组大鼠腹腔注射水杨酸钠造模并用行为学方法证实动物感受到耳鸣后,利用免疫组化方法检测各组动物耳蜗核5-HTR1B/2C、GABA、GluR1/2表达情况,并进行统计分析。结果8只注射水杨酸钠的耳鸣模型组大鼠全部造模成功。在耳鸣模型组5-HTR1B、γ-氨基丁酸(GABA)的表达显著低于Ⅰ、Ⅱ组(P<0.01);5-HTR2C、谷氨酸受体1和谷氨酸受体2(GluR1/2)表达显著高于Ⅰ、Ⅱ组(P<0.01)。Ⅰ、Ⅱ组5-HTR1B/2C、GABA、GluR1/2表达差异无统计学意义(P<0.05)。结论耳鸣模型大鼠耳蜗核中神经递质及受体发生了改变,其功能失调可能是耳鸣发生的主要机制。     

水杨酸盐诱发大鼠听皮层中TNF-α和GluA1表达的改变

目的通过检测水杨酸盐诱导耳鸣大鼠听皮层中TNF-α和AMPA受体亚基(GluA1)蛋白的表达,研究耳鸣大鼠听皮层是否出现炎症因子和膜受体表达的改变,探讨TNF-α在耳鸣中的作用机制。方法 24只SD大鼠,随机等分成4组:对照组、慢性注射7天组、慢性注射14天组、停药后恢复14天组。前脉冲抑制实验评估动物是否发生耳鸣样行为。Western Blot检测听皮层中TNF-α和GluA1蛋白表达。结果⑴长期注射水杨酸盐后,大鼠的前脉冲抑制率增加,差异有统计学意义(P<0.05)。⑵在慢性注射7天组,TNF-α和GluA1蛋白表达水平较对照组升高,差异有统计学意义(P=0.036,P=0.019,P<0.05);在慢性注射14天组,TNF-α和GluA1蛋白表达水平较对照组、停药后恢复14天组升高,差异有统计学意义(P=0.003,P=0.002,P<0.01)。⑶TNF-α和GluA1蛋白表达具有显著正相关(P=0.000,P<0.001)。结论耳鸣模型大鼠听皮层中TNF-α和GluA1蛋白表达均上调且两者变化有显著正相关性,推测TNF-α可能通过调节GluA1的表达导致大鼠耳鸣。     

补肾活血化痰开窍方对耳鸣大鼠耳蜗螺旋神经节神经元5-HT1B、2C受体表达的影响北大核心CSCD

目的探讨补肾活血化痰开窍方对耳鸣大鼠耳蜗螺旋神经节神经元(spiral ganglion neurons,SGN)中5羟色胺(serotonin,5-HT)1B、2C受体的表达及意义。方法 60只健康SPF级雄性大鼠随机分为正常组10只(生理盐水组),耳鸣模型组50只(采用水杨酸钠腹腔注射联合"饮水抑制"大鼠行为学实验方法建立大鼠耳鸣模型),耳鸣模型组造模成功后再分为水杨酸钠组10只、中药组30只(补肾活血化痰开窍方低、中、高剂量组各10只)、西药组(卡马西平组)10只,除水杨酸钠组给予生理盐水灌胃外,各组给予相应药物干预8周,造模成功后运用免疫组化法检测各组耳蜗SGN中5-HT1B、2C受体的表达。结果耳鸣造模成功并给予相应药物干预8周后,各组大鼠耳蜗SGN中均有5-HT1B、2C受体的表达,与生理盐水组相比,水杨酸钠组中5-HT1B表达减少,5-HT2C表达明显增多;与水杨酸钠组相比,中药各剂量组耳蜗SGN中5-HT1B表达增多,2C表达均明显降低。结论耳鸣大鼠耳蜗SGN中的5-HT1B受体表达减少、5-HT2C表达增加,应用补肾活血化痰开窍方后5-HT1B表达增多而5H2C表达降低,产生了拮抗作用,该方可能应用于耳鸣的治疗。     

凋亡相关蛋白Bcl-2和Bax在慢性鼻及鼻窦炎伴嗅觉障碍患者嗅黏膜中的表达

目的研究Bcl-2和Bax在慢性鼻及鼻窦炎（CRS）伴嗅觉障碍患者嗅黏膜中的表达,探讨其对嗅觉神经元（olfactory receptor neurons,ORNs）凋亡的调节作用。方法采用康涅狄格化学感受临床研究中心所采用的嗅觉检查法——CCCRC（Connecticut ChemosensoryClinical Research Center）对46例行功能性鼻内镜手术的患者进行嗅觉评分并分组：A组,CRS伴嗅觉障碍25例;B组,CRS不伴嗅觉障碍10例;C组,单纯鼻中隔偏曲行鼻中隔矫正术11例。免疫组织化学方法检测Bcl-2、Bax在3组患者嗅黏膜中的表达。结果在ORNs中,A组Bcl-2和Bax表达显著高于B组（q=3.24、4.29,P均〈0.05）和C组（q=8.56、12.99,P均〈0.01）,A组Bcl-2/Bax比值显著低于B组（q=3.76,P〈0.05）和C组（q=6.67,P〈0.01）;在基底细胞中,Bcl-2在3组表达无显著差异（q=0.68、0.69、1.06,P均〉0.05）,Bax在A组的表达显著高于B组和C组（q=9.54、11.98,P均〈0.01）,A组Bcl-2/Bax比值显著低于B组和C组（q=5.48、9.14,P均〈0.01）;在A、B、C 3组ORNs和基底细胞中,Bcl-2/Bax比值与嗅觉评分均呈正相关（rA分别为0.5631、0.8926,rB分别为0.5700、0.7991、rC分别为0.5694、0.8121,P均〈0.01）。结论细胞凋亡参与了CRS伴嗅觉障碍患者ORNs的减少,Bcl-2和Bax在此过程中起了重要的调控作用,Bcl-2/Bax比值决定细胞是否凋亡。     

外周听觉活性改变诱导在体听皮层突触NMDA受体表达变化

目的 观察听觉剥夺和耳蜗电刺激对听皮质突触N-甲基-D-天冬氨酸受体(N-methyl-D-as-partate receptor，NMDAR)表达的影响。方法 经两次不连续梯度超速离心，从初级听皮质提取高度纯化的突触体后，采用Western blotting对耳毒性聋组、听力正常组及电耳蜗内刺激0.5～2h的各实验组听皮质突触体NMDAR三个亚型的表达进行比较。结果 证实了听觉剥夺的成年或发育期大鼠耳蜗电刺激仅仅1.5小时可以诱导突触体NR2A蛋白的显著增加，但NR1和NR2B蛋白量的改变并不显著。结论 在体大鼠的听皮质存在活性依赖的突触的NR2A蛋白的表达。     

Postnatal Development of NR2A and NR2B mRNA Expression in Rat Auditory Cortex and Thalamus

Sensory cortex in the rat undergoes rapid postnatal development, especially following the onset of sensory function during so-called "critical periods." To investigate potential mechanisms in the auditory forebrain involving different NMDA receptor subunits, we have used in situ hybridization to determine expression patterns of NR2A and NR2B mRNA at postnatal days 4, 10, 13, 18, 25, and adult. In auditory cortex, NR2A mRNA expression is initially weak but increases rapidly over ~2 weeks. NR2B mRNA levels are initially high and remain high. For both subunits, expression tends to be highest in superficial layers of the cortex (except layer 1). Expression is weaker in the auditory thalamus (medial geniculate). Initially, NR2A mRNA expression is very low, whereas NR2B mRNA expression is moderate; both levels increase over ~2 weeks. Among medial geniculate subdivisions, NR2A mRNA expression occurs preferentially in the medial division, whereas NR2B mRNA expression is strongest in the ventral division. For auditory cortex and thalamus, NR2A and NR2B mRNA expression peaks about 1 week after the onset of hearing before declining slightly into adulthood. The heterogeneous distribution of NMDAR subunit mRNA throughout development may play a role in auditory forebrain development and function.     

Effects of chronic salicylate on GABAergic activity in rat inferior colliculus

It is well accepted that salicylate ototoxicity results in reversible tinnitus in humans. Salicylate-induced tinnitus may be an example of plasticity of the central auditory system and could potentially serve as a model to further understand mechanisms of tinnitus generation. This study examined levels of glutamic acid decarboxylase (GAD) and the binding characteristics of the GABA(A) receptor in auditory brainstem structures of Long-Evans rats chronically treated with salicylate. Western blotting revealed a significant 63% (P<0.008) elevation of GAD levels in the inferior colliculus (IC) of salicylate-treated subjects. This occurred in subjects demonstrating behavioral evidence of tinnitus. Muscimol saturation analysis was indicative of a salicylate-related increase in receptor affinity. Linear regression of [(3)H]muscimol saturation analysis data revealed a significant (P<0.05) reduction in K(d) values in whole IC (-48%), as well as in the central nucleus of IC (CIC, -58%) and combined external and dorsal cortex of IC (E/DCIC, -46%). The number of GABA(A) binding sites (B(max)) were also significantly (P<0.05) decreased. These changes were observed only in central auditory structures. This suggests that GAD expression and GABA(A) receptor binding characteristics may be altered with chronic exposure to sodium salicylate and these changes may represent aberrant plasticity clinically experienced as tinnitus.     

Expression of immediate-early genes in the dorsal cochlear nucleus in salicylate-induced tinnitus

Spontaneous neuronal activity in dorsal cochlear nucleus (DCN) may be involved in the physiological processes underlying salicylate-induced tinnitus. As a neuronal activity marker, immediate-early gene (IEG) expression, especially activity-dependent cytoskeletal protein (Arc/Arg3.1) and the early growth response gene-1 (Egr-1), appears to be highly correlated with sensory-evoked neuronal activity. However, their relationships with tinnitus induced by salicylate have rarely been reported in the DCN. In this study, we assessed the effect of acute and chronic salicylate treatment on the expression of N-methyl D-aspartate receptor subunit 2B (NR2B), Arg3.1, and Egr-1. We also observed ultrastructural alterations in the DCN synapses in an animal model of tinnitus. Levels of mRNA and protein expression of NR2B and Arg3.1 were increased in rats that were chronically administered salicylate (200 mg/kg, twice daily for 3, 7, or 14 days). These levels returned to baseline 14 days after cessation of treatment. However, no significant changes were observed in Egr-1 gene expression in any groups. Furthermore, rats subjected to long-term salicylate administration showed more presynaptic vesicles, thicker and longer postsynaptic densities, and increased synaptic interface curvature. Alterations of Arg3.1 and NR2B may be responsible for the changes in the synaptic ultrastructure. These changes confirm that salicylate can cause neural plasticity changes at the DCN level.     

The Effects of Salicylate on Auditory Evoked Potential Amplitwde from the Auditory Cortex and Auditory Brainstem

Tinnitus has often been studied using salicylate in animal models as they are capable of inducing tempo-rary hearing loss and tinnitus. Studies have recently observed enhancement of auditory evoked responses of the auditory cortex (AC) post salicylate treatment which is also shown to be related to tinnitus like behavior in rats. The aim of this study was to observe if enhancements of the AC post salicylate treatment are also present at structures in the brainstem. Four male Sprague Dawley rats with AC implanted electrodes were tested for both AC and auditory brainstem response (ABR) recordings pre and post 250 mg/kg intraperitone-al injections of salicylate. The responses were recorded as the peak to trough amplitudes of P1-N1 (AC), ABR wave V, and ABR waveⅡ. AC responses resulted in statistically significant enhancement of ampli-tude at 2 hours post salicylate with 90 dB stimuli tone bursts of 4, 8, 12, and 20 kHz. Wave V of ABR re-sponses at 90 dB resulted in a statistically significant reduction of amplitude 2 hours post salicylate and a mean decrease of amplitude of 31%for 16 kHz. WaveⅡamplitudes at 2 hours post treatment were signifi-cantly reduced for 4, 12, and 20 kHz stimuli at 90 dB SPL. Our results suggest that the enhancement chang-es of the AC related to salicylate induced tinnitus are generated superior to the level of the inferior colliculus and may originate in the AC.     

Salicylate- and quinine-induced tinnitus and effects of memantine

CONCLUSION: Memantine, an antiglutamatergic drug, has been proposed as a treatment for tinnitus. OBJECTIVES: The purpose of this study was to determine if memantine would prevent salicylate-induced tinnitus. Local field potentials were also recorded from auditory cortex to determine what effect salicylate, memantine, and the combination of both drugs would have on evoked potential amplitudes. MATERIALS AND METHODS: Schedule induced polydipsia-avoidance conditioning was used to identify the doses of salicylate or quinine that reliably induced tinnitus in rats. Rats were trained to lick for water during quiet intervals and avoid licking during sound intervals. RESULTS: Rats injected with saline or a low dose of sodium salicylate or quinine failed to develop tinnitus-like behaviors. However, high doses of salicylate (150-300 mg/kg/day) or quinine (100-150 mg/kg/day) greatly reduced licks-in-quiet, behavior consistent with the presence of tinnitus. Licks-in-quiet increased slightly when memantine (1.5 or 3 mg/kg/day) was co-administered with salicylate; however, the effect was not statistically significant or dose-dependent. These results indicate that memantine does not completely suppress salicylate-induced tinnitus. Cortical auditory evoked potential amplitude increased after salicylate treatment; co-administration of memantine failed to block this salicylate-induced increase.