猫耳蜗电图中N_2波起源的分析

在35只猫进行了耳蜗电图、听觉脑干电反应及耳蜗核局部电位的同时描记,将普鲁卡因或海人酸微量注入耳蜗核内,观察电位的变化,以分析耳蜗电图中N_2 波的起源。实验结果表明:猫的 N_2 波来源于外周第一级神经元冲动的成分和耳蜗核电活动的成分。     

成对短声不同间隔对单、双耳听觉脑干反应的影响——衍生听觉脑干反应方法的应用

采用具有不同间隔(0～32ms)的65dB nHL(正常听力水平)的成对短声刺激,记录20名正常人的单侧耳和两耳交替刺激的听觉脑干反应(ABR)。用计算机从成对短声反应中减去单一短声反应以提取衍生ABR。结果表明,单、双耳的衍生ABR V波振幅在成对短声间隔为0.2～1.5ms时,受到明显影响。单耳的减小54％～65％(P<0.01),两耳的减少46％～53％(P<0.01),但单、双耳的衍生ABR I波振幅未显示显著差异(P>0.05)。该结果说明,高位脑干通路在成对短声间隔为0.2～1.5ms时,不但对同侧耳的第2个短声反应能力降低,而且对来自对侧耳的第2个短声也如此。从而推断,在两耳交替刺激的耳间短声间隔小于2ms范围时,在下丘部位可能存在两耳交互作用。结果还提示,临床检查ABR时,采用的短声刺激间隔至少不应小于30ms。     

白噪声对听觉脑干电反应(ABR)和耳蜗电图(ECochG)的影响

本文通过20例听力正常人和10例听力正常豚鼠研究了白噪声对耳蜗电图(ECochG)和听觉脑干电反应(ABR)的干涉作用。实验结果表明,白噪声比短声(信号)的声强级低30dB(SL)以上时,ECochG和ABR的振幅仅轻微减小。白噪声与短声的声强级相等时,ECochG与ABR的振幅和出现率会明显受到干涉而减小,甚至完全消失。但是,此时的耳蜗微音器电位(CM)并未观察到有明显的变化。这意味着白噪声对ECochG和ABR的干涉作用主要与围绕毛细胞基底部的突触产生的抑制密切相关。由于白噪声对ABR各波的干涉有些差异,所以认为这种抑制,可能既包括脑中抑制也包括侧方抑制。     

异双核配合物[(PhPPy_2)_2PdCuCl_2]ClO_4(PhPPy_2为二(2-吡啶基)苯基膦)的合成与晶体结构

反式单核钯(Ⅱ)配合物[-Pd(PhPPy2)2Cl2](1)与ECu(CH3CN)4]ClO4反应得到异双核配合物[(PhPPy2)2PdCuCl2]ClO4·2CH3CN(2),其中金属离子由两个PhPPy2配体以一种新的模式所桥联。配合物2属于P21/c空间群,晶胞参数a、b、c分别为1.294 7(1)nm,0.914 2(1) nm和3.345 4(2)nm,β为99.698(1)°。2中的Pd(Ⅱ)和Cu(Ⅰ)离子分别为扭曲的四面体和平面正方构型。室温下,该配合物的溶液发光。     

中缝背核5-羟色胺能神经元在睡眠调节中的作用研究

目的：研究中缝背核(DRN)5-羟色胺(5-HT)能神经元在睡眠中的调节作用。方法：运用脑立体定位、核团微量注射和多导睡眠描记(PSG),观察DRN 5-HT能神经元对大鼠睡眠的影响。结果：DRN微量注射谷氨酸钠(L-Glu),大鼠睡眠减少,特别是深慢波睡眠(SWS2)明显减少,觉醒(W)增加;DRN微量注射海人酸(KA)和对氯苯丙氨酸(PCPA),大鼠SWS2和异相睡眠(PS)增加,W减少。结论：DRN 5-HT能神经元参与睡眠的调节,兴奋DRN 5-HT能神经元睡眠时间减少,抑制DRN 5-HT能神经元则具有促进睡眠的作用。     

γ-氨基丁酸对隔离皮层电活动的影响

局部施加γ-氮基丁酸(GABA)后,猫、兔的隔离皮层的电活动频率降低,振幅加大。隔离区施加五甲烯四氮唑后,癎样峰波发放仅在该区出现,且不为GABA所阻抑。有时五甲烯四氮唑可引起峰波和慢波的复合波,施加GABA可使其峰波消失,慢波加大。实验结果提示,在慢性实验中施加GABA于完整皮层表面时,皮层电活动所呈现的高幅慢波有可能起源于皮层。     

大鼠 C 类传入纤维诱发的脊髓背表面电位

实验共用大鼠66只,以激活 C 类纤维的强度刺激腓肠神经,在脊髓背表面除记录到 A 类纤维诱发的 N_1、N_2和 P_1波外,还见一长潜伏期正波。该波与 P_1波方向一致,波形类似,故称之为 P_2波。P_2波潜伏期为133.3±13.7ms, 时程为83.3±21.9ms,幅度为154.8±92.8μV.P_2波的刺激阈值(33.7±11.8T)与复合动作电位 C 波的阈值(33.1±11.8T)相同或略高,当刺激强度达87.1±15.4T 时,两者幅度同时达最大值。P_2波的潜伏期与 C 类传入抵达脊髓的时间(125.6±13.4ms)非常接近,缩短外周传导距离所致 P_2波潜伏期的缩短(39.8±5.7ms)与 C 类传入经过缩短段所需时间(38.8±5.7ms)基本一致。用直流电阻断 A 类传入仅保留 C波时,N_1、N_2、P_1波消失而 P_2波仍存在,加大阻断电流使 C 波消失时,P_2波随之消失。以上结果表明 P_2波是 C 类传入诱发的脊髓电位。脊髓横断后 P_2波并不消失,P_2波在脊髓背表面的纵向分布与 P_1波基本平行,注射印防己碱后 P_2波与 P_1波都有减小,说明 P_2波的性质与 P_1波类似,可能是 C 类传入主要经脊髓环路诱发的初级传入末梢去极化,或许可作为突触前抑制指标。     

褪黑素对海人酸致痫大鼠海马内TGF-β3水平的影响

目的探讨褪黑素(me1atonin,MT)对海人酸(kainic acid,KA)致痫大鼠海马内TGF-β3的影响,进一步明确其在中枢内的作用。方法将实验大鼠随机分为3组:生理盐水对照组(NS组)、海人酸组(KA组)、褪黑素+海人酸组(MT+KA组)。各组大鼠给予相应试剂处理后观察并记录大鼠行为学改变,用免疫组织化学方法、RT-PCR检测大鼠海马内TGF-β3(transforming growth factor-β3)的表达情况及其mRNA变化。结果动物行为学观察显示,NS组无癫痫发作,KA组发作程度为Ⅲ-V级,MT+KA组为0-Ⅲ级;免疫组织化学结果显示,TGF-β3在3组大鼠海马内均有表达,其中KA组、MT+KA组较NS组表达增强,MT+KA组较KA组增强,差异具有显著性意义(P0.05);RT-PCR结果显示,与NS组相比较,KA组、MT+KA组大鼠海马内TGF-β3 mRNA含量均升高;但MT+KA组升高较KA组多,差异具有显著性意义(P0.05)。结论褪黑素能明显改善海人酸诱发的大鼠癫痫,增强海马内TGF-β3的表达,减轻海马神经元损伤,发挥中枢保护作用。     

青年猫与老年猫初级听皮层GABA_A受体免疫表达的比较研究

目的对5只老年猫(12岁,3-3.5kg)与5只青年猫(2岁,3-3.5kg)初级听皮层(AI)γ-氨基丁酸(gamma-aminobutyric acid,GABA)A受体神经元进行免疫表达比较研究,探索老年猫与青年猫初级听皮层(AI)GABAA受体年龄性变化及产生可影响的生理作用。方法运用免疫组织化学反应与免疫印迹相结合的方法对不同年龄组动物(AI)组织进行染色。光学显微镜下观察、拍照;免疫组织化学阳性反应示GABAA R-IR(GABAA receptor-immunoreaction)神经元形态、密度及分布;免疫印迹示GABAA受体蛋白含量变化。结果老年猫的AI区GABAA R-IR神经元密度比青年猫的GABAA R-IR下降了29.19%,阳性反应强度减弱了20.7%,老年猫阳性反应细胞占神经元总数百分比比青年猫的减少了5.32%;老年猫的GABAA受体蛋白表达量比青年猫的下降了23.16%。结论初级听皮层GABAA受体细胞及受体表达下调可能是老年个体听觉功能减退的重要原因。     

Enhancement and Distortion in the Temporal Representation of Sounds in the Ventral Cochlear Nucleus of Chinchillas and Cats

A subset of neurons in the cochlear nucleus (CN) of the auditory brainstem has the ability to enhance the auditory nerve''s temporal representation of stimulating sounds. These neurons reside in the ventral region of the CN (VCN) and are usually known as highly synchronized, or high-sync, neurons. Most published reports about the existence and properties of high-sync neurons are based on recordings performed on a VCN output tract—not the VCN itself—of cats. In other species, comprehensive studies detailing the properties of high-sync neurons, or even acknowledging their existence, are missing.Examination of the responses of a population of VCN neurons in chinchillas revealed that a subset of those neurons have temporal properties similar to high-sync neurons in the cat. Phase locking and entrainment—the ability of a neuron to fire action potentials at a certain stimulus phase and at almost every stimulus period, respectively—have similar maximum values in cats and chinchillas. Ranges of characteristic frequencies for high-sync neurons in chinchillas and cats extend up to 600 and 1000 Hz, respectively. Enhancement of temporal processing relative to auditory nerve fibers (ANFs), which has been shown previously in cats using tonal and white-noise stimuli, is also demonstrated here in the responses of VCN neurons to synthetic and spoken vowel sounds.Along with the large amount of phase locking displayed by some VCN neurons there occurs a deterioration in the spectral representation of the stimuli (tones or vowels). High-sync neurons exhibit a greater distortion in their responses to tones or vowels than do other types of VCN neurons and auditory nerve fibers.Standard deviations of first-spike latency measured in responses of high-sync neurons are lower than similar values measured in ANFs'' responses. This might indicate a role of high-sync neurons in other tasks beyond sound localization.     

脑干缺血对听觉脑干反应影响的实验研究

目的 :探讨脑干缺血模型ABR变化特点及其在脑缺血早期诊断中的应用价值。方法 :阻断猫基底动脉不同部位血流 ,观察记录阻断血流后不同时间ABR变化特点及其规律。结果 :①夹闭基底动脉上、下段或小脑下前动脉 10min左右 ,ABRP3 ,P4振幅明显减小 (P <0 .0 1,P <0 .0 5 ) ,60min恢复夹前水平 ;②夹闭基底动脉上段 10～60minP5明显减小 (P <0 .0 5 ) ,直到 12 0min尚未恢复至夹前状态。结论 :①猫的ABRP3脑区的血供主要来自小脑下前动脉 ,P1,P2产生部位基本不依赖基底动脉供血 ;②轻度暂短性脑缺血时ABR振幅比潜伏期更敏感 ,振幅减小的程度与脑干缺血的程度密切相关 ;③ABR可用于脑缺血定位诊断及脑功能动态观察的电生理检测。     

丹参注射液对链霉素耳中毒豚鼠耳蜗iNOS表达的影响

目的: 探讨链霉素(SM)耳中毒过程中豚鼠耳蜗iNOS表达,以及丹参注射液(DS)的拮抗作用.方法: 应用光镜、电镜、免疫组化及图像分析技术,结合听性脑干反应(ABR)测试.结果: 用药10d后,SM组ABR阈值明显升高,DS SM组ABR阈值明显低于SM组,差异显著(P<0.01).光镜及电镜下可见SM组柯蒂氏器、内外毛细胞、螺旋神经节细胞、血管纹损伤严重,DS SM组损伤较轻.SM组iNOS在柯蒂氏器、内外毛细胞、螺旋神经节、血管纹的表达明显高于DS SM组.结论: SM耳中毒时ABR阈值升高,iNOS表达增强.DS能有效的降低SM所致的ABR阈值升高,并抑制iNOS的过量表达,从而减轻SM的耳毒性损伤,提示DS对SM耳毒性损伤有保护作用.     

Neuroanatomical technique for studying long axonal projections in the central nervous system: combined axonal staining and pre-labeling in parasagittal gerbil brain slices

A method is described for studying the morphological features of extensive axonal projections within the central nervous system of the gerbil, Meriones anguiculatus. Potentially long descending axonal projections between the auditory thalamus and lower brainstem were used as a model. The inferior colliculus (IC) in the tectum was injected in vivo with a fluorescent retrograde tracer, Fluoro-Gold, to label cells in the medial geniculate body (MGB) that had descending projections to the IC, and cells in the superior olivary complex (SOC) that had ascending projections to the IC. Another fluorescent retrograde tracer, fast blue, was injected into the cochlea to label olivocochlear (OC) cells in the SOC. Inferomedially curved parasagittal slices containing ipsilateral auditory cell groups from the thalamus to the brainstem were cut and descending axons of the pre-labeled MGB cells were traced anterogradely with Biocytin. After visualizing histologically the injected Biocytin, discretely labeled IC-projecting axons of the MGB cells were traced including their collaterals that extended further into the SOC. In the SOC, these axons terminated on pre-labeled cells including OC cells. The combination of anterograde and retrograde tracing in the slice preparations described here demonstrated extensive descending axonal projections from the thalamus to their targets in the lower brainstem that had known ascending/descending projections within the auditory system.     

Neurodynamics, tonality, and the auditory brainstem response

Tonal relationships are foundational in music, providing the basis upon which musical structures, such as melodies, are constructed and perceived. A recent dynamic theory of musical tonality predicts that networks of auditory neurons resonate nonlinearly to musical stimuli. Nonlinear resonance leads to stability and attraction relationships among neural frequencies, and these neural dynamics give rise to the perception of relationships among tones that we collectively refer to as tonal cognition. Because this model describes the dynamics of neural populations, it makes specific predictions about human auditory neurophysiology. Here, we show how predictions about the auditory brainstem response (ABR) are derived from the model. To illustrate, we derive a prediction about population responses to musical intervals that has been observed in the human brainstem. Our modeled ABR shows qualitative agreement with important features of the human ABR. This provides a source of evidence that fundamental principles of auditory neurodynamics might underlie the perception of tonal relationships, and forces reevaluation of the role of learning and enculturation in tonal cognition.     

Restoration of Hearing in the VGLUT3 Knockout Mouse Using Virally Mediated Gene Therapy

Mice lacking the vesicular glutamate transporter-3 (VGLUT3) are congenitally deaf due to loss of glutamate release at the inner hair cell afferent synapse. Cochlear delivery of VGLUT3 using adeno-associated virus type 1 (AAV1) leads to transgene expression in only inner hair cells (IHCs), despite broader viral uptake. Within 2?weeks of AAV1-VGLUT3 delivery, auditory brainstem response (ABR) thresholds normalize, along with partial rescue of the startle response. Lastly, we demonstrate partial reversal of the morphologic changes seen within the afferent IHC ribbon synapse. These findings represent?a successful restoration of hearing by gene replacement in mice, which is a significant advance toward gene therapy of human deafness.     

Differential expression pattern of chloride transporters<Emphasis Type="Italic"> NCC,NKCC2, KCC1, KCC3, KCC4,</Emphasis> and<Emphasis Type="Italic"> AE3</Emphasis> in the developing rat auditory brainstem

During development of inhibitory synapses, the action of the two neurotransmitters GABA and glycine shifts from depolarizing to hyperpolarizing. The shift is due to an age-dependent regulation of the intracellular free chloride concentration ([Cl(-)](i)) in postsynaptic neurons. A model system to study this maturation process is a glycinergic projection in the mammalian auditory brainstem. It is formed in the superior olivary complex (SOC) by neurons of the medial nucleus of the trapezoid body, whose axons terminate in the lateral superior olive (LSO). LSO neurons of perinatal rats and mice are depolarized upon glycine application, whereas older cells (>postnatal day (P) 8) are hyperpolarized. Here we examined the expression of six secondary active chloride transporter genes ( NCC, NKCC2, KCC1, KCC3, KCC4, and AE3) in the rat SOC to unravel the molecular mechanisms underlying this change. RT-PCR analysis demonstrated brainstem expression of KCC1, KCC3, KCC4, and AE3, but not of NCC and NKCC2. RNA in situ hybridization showed that only AE3 is highly expressed both at P3 (high [Cl(-)](i)) and P12 (low [Cl(-)](i)) in LSO neurons. KCC1 and KCC4 are weakly expressed in LSO neurons at P3 and P12, respectively. This study completes the expression analysis of all known chloride transporters sensitive to loop diuretic drugs in the SOC and demonstrates differences in the maturation between hippocampal and brainstem inhibitory synapses.     

Egr2::Cre Mediated Conditional Ablation of Dicer Disrupts Histogenesis of Mammalian Central Auditory Nuclei

Histogenesis of the auditory system requires extensive molecular orchestration. Recently, Dicer1, an essential gene for generation of microRNAs, and miR-96 were shown to be important for development of the peripheral auditory system. Here, we investigated their role for the formation of the auditory brainstem. Egr2::Cre-mediated early embryonic ablation of Dicer1 caused severe disruption of auditory brainstem structures. In adult animals, the volume of the cochlear nucleus complex (CNC) was reduced by 73.5%. This decrease is in part attributed to the lack of the microneuronal shell. In contrast, fusiform cells, which similar to the granular cells of the microneural shell are derived from Egr2 positive cells, were still present. The volume reduction of the CNC was already present at birth (67.2% decrease). The superior olivary complex was also drastically affected in these mice. Nissl staining as well as Vglut1 and Calbindin 1 immunolabeling revealed that principal SOC nuclei such as the medial nucleus of the trapezoid body and the lateral superior olive were absent. Only choline acetyltransferase positive neurons of the olivocochlear bundle were observed as a densely packed cell group in the ventrolateral area of the SOC. Mid-embryonic ablation of Dicer1 in the ventral cochlear nucleus by Atoh7::Cre-mediated recombination resulted in normal formation of the cochlear nucleus complex, indicating an early embryonic requirement of Dicer1. Quantitative RT-PCR analysis of miR-96 demonstrated low expression in the embryonic brainstem and up-regulation thereafter, suggesting that other microRNAs are required for proper histogenesis of the auditory brainstem. Together our data identify a critical role of Dicer activity during embryonic development of the auditory brainstem.