EFFERENT INNERVATION OF IDENTIFIED VESTIBULAR AFFERENTS

本研究的目的是探讨前庭末梢器的传出神经支配。 了解脑干传出神经元到外周迷路的神经递质和投射将有助于我们理解前庭传出系统在健康和疾病中的作用。 最近的研究表明，前庭传出核神经元的递质成分和外周靶点是异质的。 这种异质性改变了我们长期以来认为前庭传出神经是一种非特异性系统的观点。 本研究的目的是根据毛丝鼠的脑干位置、投射模式、外周末梢、神经递质及其受体亚型来确定毛丝鼠传出神经元的亚群。 具体目标是：1）通过结合逆行和顺行示踪剂与递质免疫组织化学来表征脑干传出神经元的解剖学和神经化学亚群，以及2）在光镜和电镜水平上确定外周传出神经元的形态学终止的细节，以及通过确定其递质受体亚型在分子水平上确定其神经化学的细节。 脑干中的传出神经元通过逆行示踪剂注射到外周前庭器官中来识别。 它们同时用几种假定的神经递质（乙酰胆碱、降钙素基因相关肽、一氧化氮合酶、甲硫氨酸脑啡肽、三磷酸腺苷等）的抗体进行化学表征。 在外围，受体亚型的分布肽能，嘌呤能和毒蕈碱传输将被检查，试图具体了解传入传出刺激的缓慢反应。 前庭传入通过细胞外辣根过氧化物酶注射或calretinin免疫组织化学的手段。 外周传出神经末梢的神经支配模式由生物素化葡聚糖胺中枢注射决定。 电子显微镜免疫组织化学方法被用来表征化学不同的传出终扣根据其终端的感觉上皮，也就是说，由类传入（花萼，二形或终扣）和区域（中央或周边区），他们支配。 其目的是产生一个关于传出神经的结构基础的知识体系，以及它们与传入神经的关系，从中可以得出生理学和可验证的假设。

The purpose of this grant is to investigate the efferent innervation of the peripheral vestibular apparatus. Knowledge of the neurotransmitters and the projections from the brainstem efferent neurons to the peripheral labyrinth will help us understand the role of the vestibular efferent system in health and disease. Recent studies have suggested that neurons in the vestibular efferent nucleus are heterogeneous in their transmitter composition and in their peripheral targets. Such heterogeneity changes our long-held view that vestibular efferents are a nonspecific system. The goal of this study is to define subpopulations of efferent neurons in the chinchilla based upon their brain stem locations, their projection patterns, their peripheral endings, their neurotransmitters, and their receptor subtypes. Specific aims are: 1) to characterize anatomical and neurochemical subpopulations of brainstem efferent neurons by combining retrograde and anterograde tracers with transmitter immunohistochemistry, and 2) to determine details of the morphological terminations of efferents in the periphery, at both the light and electron microscopic levels, and details of their neurochemistry at the molecular level by determining their transmitter receptor subtypes. Efferent neurons in the brainstem are identified by means of retrograde tracer injections into the peripheral vestibular apparatus. They are simultaneously characterized immunohistochemically with antibodies to several putative neurotransmitters (acetylcholine, calcitonin gene- related peptide, nitric oxide synthase, met-enkephalin, adenosine triphosphate, and others). In the periphery, the distribution of receptor sub-types for peptidergic, purinergic and muscarinic transmission will be examined in an attempt to specifically understand the slow response of afferents to efferent stimulation. Vestibular afferents are identified by means of extracellular horseradish peroxidase injections or calretinin immunohistochemistry. The innervation patterns of efferent terminals in the periphery is determined by injections of biotinylated dextran amine centrally. Electron microscopic immunohistochemical methods are used to characterize chemically distinct efferent boutons according to their terminations in the sensory epithelium, that is, by the class of afferents (calyx, dimorphic or bouton) and by the region (central or peripheral zones) that they innervate. The intent is to produce a body of knowledge about the structural basis of the efferents, and their relationship to the afferents, from which physiologically and pharmacologically testable hypotheses can be derived.