中缝背核至内耳投射的神经生物学标记

目的我们的前期研究表明中缝背核(dorsal raphe nucleus,DRN)和内耳之间存在传出神经联系。本研究的目的是探讨DRN向耳蜗的投射方式。方法将示踪剂生物素化葡聚糖胺(Biotinylated Dextrain Amine,BDA)注入猫的DRN区,10天后处死动物,取出耳蜗,行BDA染色,内耳毛细胞铺片。结果 1.在第一、二排外毛细胞内可见散在的BDA阳性的呈棕褐色深染的毛细胞,分布不规则,未见显色的内毛细胞。2.可见来自蜗轴方向的纤维向外毛细胞底部投射。结论中缝背核与耳蜗外毛细胞之间可能存在一种纤维联系;这一联系主要存在于第一、二排外毛细胞。     

从中缝背核向内耳的多巴胺能投射

目的 探讨中缝背核至内耳的传出神经通路。方法 选择耳廓反射灵敏，体重2～3kg没有中耳疾病的健康猫11只，分为实验组（8只）和对照组（3只）。经内耳注射逆行示踪剂霍乱毒素亚型B，7d后处死，脑干连续切片，免疫荧光染色，获得中缝背核区内逆行荧光标记后，将组织分成4组，分别用兔抗-酪氨酸羟化酶、兔抗-5-羟色胺、兔抗-γ-氨基丁酸和兔抗-多巴胺-β-羟化酶对中缝背核区内神经细胞进行免疫荧光标记研究。结果 ①沿着脑桥的尾端（耳蜗核水平）向中脑的嘴侧观察连续切片，可见霍乱毒素亚型B红色荧光标记细胞主要分布在脑干中线周围的背侧区域即中缝背核区域；②将上述组织切片用抗酪氨酸羟化酶、5-羟色胺、1-氨基丁酸和多巴胺-β-羟化酶4种荧光抗体进行第2次标记后，发现在中缝背核区域内均分布有上述4种神经元，其中酪氨酸羟化酶标记神经元和经内耳至中缝背核区的逆行标记全部为双标记荧光细胞，5-羟色胺、γ-氨基丁酸和多巴胺-β-羟化酶均为单标记。由此提示，中缝背核向内耳传出投射与酪氨酸羟化酶标记神经元有关。结论 中缝背核和内耳之间存在传出神经联系；这一投射可能主要是多巴胺能投射。     

听觉传出神经系统研究进展

听觉传出神经在维持听觉高敏感度及分辨力、听觉调控及听觉防护等各方面起着十分重要的作用。听觉传出神经通路作为听觉系统重要的投射体系之一,橄榄耳蜗束是乞今为止已被证实存在的唯一的听觉传出神经通路;最近有学者提出,可能存在中缝背核-迷路听觉传出神经通路。     

与听觉、前庭系统相关的中缝背核神经通路研究进展

中缝背核（dorsal raphe nucleus，DRN）是中缝核中8个缝核之一，对听觉和前庭刺激可以做出反应，投射到大脑皮质广泛区域、基底核和间脑．并可以与听觉和前庭通路的许多部分组成神经纤维联系。本文将近年来中缝背核与听觉、前庭相关神经通路研究综述如下。     

豚鼠corti器和脑干下部听觉通路CGRP的免疫组化定位研究

采用ABC-葡萄糖氧化酶-DAB-镍(ABC-GDN)免疫组化技术研究了降钙素基因相关肽免疫反应(CGRP-IR)在豚鼠Corti器和脑干下部听觉通路的分布,发现内、外毛细胞区均可见大量的阳性神经末梢,后者越向顶转、越向外排毛细胞越少。螺旋神经节内可见阳性神经束,而神经节细胞呈阴性反应。耳蜗背侧和腹侧核内有CGRP-IR阳性纤维;内侧和外侧上橄榄核均有CGRP-IR阳性神经元胞体。结果提示Corti器含CGRP神经为耳蜗传出神经,CGRP可能参与神经信息的传递。     

内、外侧橄榄耳蜗束的分离及其对耳蜗功能的影响

听觉传出神经通路是听觉系统重要的投射体系之一,而橄榄耳蜗束(olivocochlear bundle,OCB)是唯一已被证实的听觉传出神经通路,包括内侧橄榄耳蜗束(medial olivocochlear,MOC)和外侧橄榄耳蜗束(lateral olive cochlear,LOC)两部分。近年来,许多学者试图用电刺激、解剖学分离和药理学分离     

逆行荧光标记观察猫上橄榄复合体向内耳的投射

目的 探讨猫橄榄耳蜗神经元的分布和向内耳的投射特征.方法 11只成年猫随机分为两组,实验组8只,左侧耳蜗鼓阶内注射1%霍乱毒素B亚单位,右侧耳蜗鼓阶注射5%荧光金,对照组3只,双侧耳蜗均注射生理盐水.动物饲养7 d后处死,脑干连续冰冻切片,免疫荧光处理,荧光显微镜观察被标记的橄榄耳蜗神经元.结果 实验组每只动物被霍乱毒素B亚单位和荧光金标记的橄榄耳蜗神经元平均总数为(3210±168)个,分为外侧橄榄耳蜗神经元[(2298±120)个]和内侧橄榄耳蜗神经元[(913±64)个].根据投射特征可将被标记的神经元分为三种不同类型:只投射到同侧耳蜗的神经元,只投射到对侧耳蜗的神经元,既向同侧又向对侧耳蜗投射的双标记神经元,其中双标记神经元在外侧橄榄耳蜗神经元和内侧橄榄耳蜗神经元中分别占3.9%和15.1%.对照组未观察到被标记的檄榄耳蜗神经元.结论猫的橄榄耳蜗系统中存在三种不同投射特征的神经元,其中双侧投射的神经元在外侧橄榄耳蜗神经元和内侧橄榄耳蜗神经元中均有分布.     

小动物内耳影像学研究进展

<正>内耳又称为迷路,内部结构复杂,由骨迷路和膜迷路构成。内耳解剖结构的完整是听觉形成的物理基础。耳蜗是内耳的重要结构之一,耳蜗对声音具有高度敏感性和高度选择性,任何引起耳蜗结构和功能改变的疾病都会导致不同程度的听力下降。耳蜗中最重要的是柯蒂氏器(organ of Corti),Corti氏器由听毛细胞支持细胞和和盖膜所组成[1]。耳蜗内有听觉通路第一级神经元,一级神经元的树突始于Corti氏器听毛细胞的基底,轴突延伸成为耳蜗神经,     

降钙素基因相关肽在豚鼠耳蜗中的分布

目的：观察降钙素基因相关肽(CGRP)在成年豚鼠耳蜗中的分布。方法：采用免疫组织化学，光镜观察的方法，对CGRP在豚鼠耳蜗中的分布进行研究。结果：CGRP阳性反应物分布于螺旋神经元．骨螺旋板神经孔，内毛细胞、外毛细胞与外支持细胞交界区，螺旋韧带血管纹。结论：CGRP广泛分布于豚鼠耳蜗，是耳蜗传出神经系统重要的神经递质或神经凋质，CGRP可能通过调节螺旋神经元、毛细胞和支持细胞等影响听功能．也可能影响耳蜗的血流。     

声音激发第八对脑神经和脑干反应(耳蜗电图)--猫实验的观察。

作者使用叠加技术对猫进行电生理学的实验。在猫的听觉通路各水平,用电凝固法进行损害,术前术后用声音刺激产生的电位记录下来,并将猫的脑干作连续切片观察病变范围,从比较中提出一些看法。结果--(1) 破坏一例耳蜗,其患侧耳在各种强度均无反应,只是在100分贝的刺激可见曲线的早期部分有电磁干挠波,而且出现ⅣV波,这是对侧正常耳的听觉。而在对侧正常耳,     

Connections between the Dorsal Raphe Nucleus and a Hindbrain Region Consisting of the Cochlear Nucleus and Neighboring Structures

Previous studies have shown that neurons in the raphe nuclei respond to acoustic stimuli. The present study investigated connections between the dorsal raphe nucleus (DRN) and a hindbrain region consisting of the cochlear nucleus (CN) and neighboring structures. A mixture of one or more tracers (cholera toxin B, biotinylated dextran amine (BDA), and 3H-leucine) was injected into the cat DRN. Retrograde-labeling results are presented whereby a new structure, to be called the juxta-acoustico-floccular fascicle (JAFF), is identified. The JAFF is surrounded by the CN, flocculus, lateral cerebellar nucleus, lateral vestibular nucleus, and restiform body. The JAFF is closely associated with the infracerebellar nucleus (ICN). Labeled neurons projecting to the DRN were concentrated in the JAFF, embedded among axons. Less numerous labeled neurons were in the ICN and CN. Anterograde-labeling results are presented showing fibers labeled with BDA or with BDA and ³H-leucine in the CN, cochlear nerve and vestibular nerve, indicating that the DRN projects to these structures. The ascending and descending connections between the DRN and the above hindbrain region may mediate a reflex that may alter the sensitivity of the auditory system in response to biologically salient (e.g. threatening or attractive) stimuli.     

Connections between the dorsal raphe nucleus and a hindbrain region consisting of the cochlear nucleus and neighboring structures

Previous studies have shown that neurons in the raphe nuclei respond to acoustic stimuli. The present study investigated connections between the dorsal raphe nucleus (DRN) and a hindbrain region consisting of the cochlear nucleus (CN) and neighboring structures. A mixture of one or more tracers (cholera toxin B, biotinylated dextran amine (BDA), and 3H-leucine) was injected into the cat DRN. Retrograde-labeling results are presented whereby a new structure, to be called the juxta-acoustico-floccular fascicle (JAFF), is identified. The JAFF is surrounded by the CN, flocculus, lateral cerebellar nucleus, lateral vestibular nucleus, and restiform body. The JAFF is closely associated with the infracerebellar nucleus (ICN). Labeled neurons projecting to the DRN were concentrated in the JAFF, embedded among axons. Less numerous labeled neurons were in the ICN and CN. Anterograde-labeling results are presented showing fibers labeled with BDA or with BDA and 3H-leucine in the CN, cochlear nerve and vestibular nerve, indicating that the DRN projects to these structures. The ascending and descending connections between the DRN and the above hindbrain region may mediate a reflex that may alter the sensitivity of the auditory system in response to biologically salient (e.g. threatening or attractive) stimuli.     

Immunohistochemical study for monoamine neurons in the brain of unilateral inner ear impaired rats

Patients with inner ear impairment have complaints of vertigo and also occasionally depression. The present study was undertaken in order to evaluate changes in monoamines which have reportedly been closely related to depression, using cisplatin-induced unilateral inner-ear impaired rats. A dose of 0.5 mg/kg of cisplatin was injected into the right tympanic cavity under pentobarbital Na+ anesthesia. One or two weeks later, animals were fixed with paraformaldehyde, and thereafter immunohistochemical stainings for monoamine-containing cells in the brain were carried out. To visualize 5-hydroxytryptamine (5-HT), noradrenaline (NA) and dopamine (DA) neurons, we used mouse antibodies against 5-HT, NA, and DA syntheses, i.e., tryptophan hydroxylase (TRH), tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH). The number of TRH immunoreactive neurons significantly decreased in the lateral dorsal raphe nucleus of the ipsilateral side when compared with the contralateral side. The number of DA neurons, which were immunoreactive to TH, but not to DBH, significantly decreased in the hypothalamus of the ipsilateral side. The number of NA neurons which were immunoreactive to both TH and DBH significantly decreased in the locus coeruleus and ventral lateral pons of the ipsilateral side. An additional control study with saline-injected rats showed a lack of differences in monoamine syntheses between the injected and contralateral sides, the expressions of the synthesis on both sides being similar to that obtained in the contralateral side in cisplatin-injected rats. These results indicated the decreases in monoamine syntheses at the ipsilateral side only in the cisplatin-administered rats. We conclude that inner ear impairment may diminish the ipsilateral amount of monoamines in the brain but not the cotralateral, possibly inducing a vestibular compensation such as an upregulation of monoamine receptors.     

Organization and connections of the dorsal descending nucleus and other presumed acoustic areas in the brainstem of the teleost fish, Astronotus ocellatus

This study provides new information on brainstem areas, assumed to be auditory based on observations in other species, in the oscar, Astronotus ocellatus. The primary goal of the study was to explore the morphology of the dorsal descending octaval nucleus, which contains a population of neurons that receives acoustic afferents from the inner ear. Using cytoarchitectonic and connectional criteria, we revised the previously defined dorsal boundary of the descending octaval nucleus, such that the most dorsomedial neurons in this nucleus are positioned ventral to the cerebellar crest and medial to nucleus medialis. At some levels, these dorsomedial cells are continuous with another part of the dorsal descending nucleus that underlies nucleus medialis. The terminal fields of the saccule and lagena are located within this latter, more ventral part of the dorsal descending nucleus. However, the dorsomedial cells that are proximate to the cerebellar crest have long ventral dendrites that extend into these terminal fields, and therefore likely receive saccular and lagenar input. In contrast to a previous report, saccular afferents terminate more medially within the dorsal descending nucleus than do lagenar inputs. Injections of horseradish peroxidase in nucleus centralis of the torus semicircularis revealed that many descending nucleus neurons that lie within the saccular and lagenar terminal fields, including the dorsomedial neurons proximate to the cerebellar crest, project to this acoustic midbrain area. These injections also revealed a secondary octaval population like that described in otophysan fishes.     

Transsynaptic delivery of nanoparticles to the central auditory nervous system

CONCLUSION: Silica nanoparticles may serve as a nonviral delivery system to the sensory hair cells, spiral ganglion cells within the cochlea, and the vestibular organ, as well as the cochlear nucleus. OBJECTIVES: At present there are no targeted therapeutics for inner ear disease. A variety of viral vector systems have been tested in the inner ear with variable efficacy but they are still not regarded as safe systems for inner ear delivery. Nanoparticles are a nonviral method of delivering a variety of macromolecules that potentially can be used for delivery within the auditory system. In this study, we evaluated the distribution and safety of nanoparticles in the inner ear. MATERIALS AND METHODS: Cy3-labeled silica nanoparticles were placed on the round window membrane of adult mice. Hearing thresholds were determined after nanoparticle delivery by auditory brainstem responses (ABRs). Distribution of particles was determined by histological evaluation of the cochlea, vestibular organs, and brain stem. RESULTS: Fluorescent microscopy demonstrated Cy3-labeled nanoparticles signals in the sensory hair cells and the spiral ganglion neurons of both the treated and contralateral inner ears. Additionally, the distal part of the central auditory pathway (dorsal cochlear nucleus, superior olivary complex) was found to be labeled with the Cy3-linked silica nanoparticles, indicating a retrograde axonal transport. No hearing loss or inflammation was noted in the treated cochlea.     

Transsynaptic delivery of nanoparticles to the central auditory nervous system

Conclusion. Silica nanoparticles may serve as a nonviral delivery system to the sensory hair cells, spiral ganglion cells within the cochlea, and the vestibular organ, as well as the cochlear nucleus. Objectives. At present there are no targeted therapeutics for inner ear disease. A variety of viral vector systems have been tested in the inner ear with variable efficacy but they are still not regarded as safe systems for inner ear delivery. Nanoparticles are a nonviral method of delivering a variety of macromolecules that potentially can be used for delivery within the auditory system. In this study, we evaluated the distribution and safety of nanoparticles in the inner ear. Materials and methods. Cy3-labeled silica nanoparticles were placed on the round window membrane of adult mice. Hearing thresholds were determined after nanoparticle delivery by auditory brainstem responses (ABRs). Distribution of particles was determined by histological evaluation of the cochlea, vestibular organs, and brain stem. Results. Fluorescent microscopy demonstrated Cy3-labeled nanoparticles signals in the sensory hair cells and the spiral ganglion neurons of both the treated and contralateral inner ears. Additionally, the distal part of the central auditory pathway (dorsal cochlear nucleus, superior olivary complex) was found to be labeled with the Cy3-linked silica nanoparticles, indicating a retrograde axonal transport. No hearing loss or inflammation was noted in the treated cochlea.     

Organization of Olivocochlear Neurons in the Cat Studied with the Retrograde Tracer Cholera Toxin-B

We employed cholera toxin-B (CTB), an efficient retrograde tracer, to examine olivocochlear (OC) neurons in the cat. Our primary goals were (1) to determine whether the cat has two types of lateral OC (LOC) neurons as is found in certain rodents and (2) to document the morphology, number, and caudorostral distribution of OC neurons, bilaterally. Adult cats received injections of CTB through the round window of the left cochlea, and, after 3–6 days, the brains were sectioned transversely and CTB was revealed immunocytochemically in every section. In three cats, OC neurons were mapped, counted differentially according to cell group, and the numbers of each plotted bilaterally from caudal to rostral. In one cat, measurements were made on labeled LOC and medial OC (MOC) neurons. The results indicate that LOC neurons can be divided into two groups based on their proximity to the lateral superior olive (LSO): a more populous group of small neurons that have intimate contact with the LSO, designated marginal-LOC neurons, and a less populous, morphologically heterogeneous group, lying more distantly from the LSO, designated para-LOC neurons. Para-LOC neurons lying dorsal and rostral to LSO were significantly larger than marginal-LOC. We hypothesize that the cat marginal-LOC neurons and most probably the larger para-LOC neurons correspond to rodent intrinsic and shell LOC neurons, respectively, which have focal versus diffuse projections beneath the inner hair cells. Concerning MOC neurons, we confirm and extend previous observations on the clustering of these neurons near the rostral tip of the medial superior olivary nucleus and also show that MOC neurons differ in size according to cell group. Finally, we compare the present counts of OC neurons (mean total 1607, consisting of 1058 LOC neurons and 549 MOC neurons innervating one cochlea) and their proportional distribution ipsilaterally and contralaterally with those reported previously. Our estimate of the number of LOC neurons is somewhat higher than those previously obtained either by retrograde labeling with horseradish peroxidase or by counting unmyelinated axons in the olivocochlear bundle. In contrast, our estimate of the number of MOC neurons is very similar to those previously reported.     

A nitrergic projection from the superior olivary complex to the inferior colliculus of the rat

The present study was conducted to test whether the ascending auditory projection from the superior olivary complex (SOC) of the brainstem to the inferior colliculus (IC) may use nitric oxide (NO) as a neuroactive compound. We identified olivo-collicular projection neurons in subnuclei of the SOC by retrograde neuronal tracing with Fluoro-Gold (FG) injected into the central nucleus of the IC. Sections containing retrograde labelled neurons were subjected to immunohistochemical incubation in an antiserum directed against the enzyme responsible for NO production in nerve cells, neuronal NO synthase (nNOS). The analysis showed that FG-containing neurons as well as nNOS-immunoreactive neurons were present in the lateral superior olive (LSO), superior paraolivary nucleus (SPO), ventral nucleus of the trapezoid body (VNTB), medial superior olive (MSO) and in dorsal and ventral periolivary regions to different amounts. However, only in the LSO, SPO and VNTB double-labelled neurons were found. They made up to less than 10% of all nNOS neurons in the SOC. Considering that only about 5% of the nNOS cells in the SOC are olivocochlear neurons [Riemann and Reuss, 1999], it is still open whether the majority of nitrergic neurons of the SOC project to other sites or whether they rather have intrinsic actions in providing NO to the SOC.     

Glycine immunoreactive projections from the dorsal to the anteroventral cochlear nucleus.

The aim of the present study was to investigate whether projections from the dorsal cochlear nucleus (DCN) to the anteroventral cochlear nucleus (AVCN) use either of two inhibitory transmitters, glycine or GABA. Retrograde HRP labeling of DCN-to-AVCN projection neurons was combined with postembedding immunocytochemistry in the DCN of guinea pigs. Following injections of HRP in the anterior or posterior divisions of AVCN, large numbers of neurons were labeled in the DCN. All of these were located in the deep layer, except for a few granule cells. Nearly all (96%) of the projection neurons were immunoreactive for glycine and most had dendritic and somatic morphologies corresponding to those of elongate neurons (so-called 'corn' cells); only a few resembled small stellate neurons. Few (3%) retrogradely labeled neurons were immunoreactive for GABA. The results suggest that projections from the deep DCN to the AVCN are formed primarily by glycinergic elongate neurons. These projections could have a substantial inhibitory influence on the output of neurons in the AVCN.