Molecular biology of cochlear efferent receptors

描述（由申请人提供）：所有毛细胞系统，包括侧线器官、前庭器官和耳蜗，都包含传出神经支配，起源于脑干并投射到毛细胞和/或感觉上皮中的神经元件。在哺乳动物耳蜗中，这种传出系统起源于上橄榄复合体，被称为橄榄耳蜗（OC）通路，由内侧（MOC）和外侧（LOC）组成。耳蜗传出神经可能有两种功能：防止声学过度刺激和增强背景噪声下的声音识别能力。在上一个项目期间，我们确定MOC传出可以通过新发现的α 9/10 nACh受体复合物保护耳蜗免受声学过度刺激。在接下来的项目期间，我们将重点研究含有降钙素基因相关肽（CGRP）的LOC传出纤维。我们确定敲除小鼠CGRP的缺失减少了耳蜗神经的声音诱发活动，这将导致声音感知的动态范围的减少。然而，毛细胞器官中有几个cgrp能神经元系统：传出以及支配脉管系统的通路，这可能有助于听觉表型。我们的目标是确定从传出纤维释放的CGRP影响神经元传入的分子机制。在这些目标中，我们将(1)确定CGRP受体信号传导对声诱发活动的影响；(2)确定CGRP受体信号转导的生化时间过程；(3)确定CGRP受体信号传导的生理靶细胞。我们将使用腺病毒基因转移、DPOAE、ABR和CAP检测听觉功能、免疫组织化学、共免疫沉淀、生物转染和FRET成像来实现这些目标。从这些研究中获得的信息将直接评估CGRP传出反馈通路用于增强耳蜗神经声音诱发活动的分子机制。

DESCRIPTION (provided by applicant): All hair cell systems, including lateral-line organs, vestibular organs and the cochlea, contain an efferent innervations, originating in the brainstem and projecting to the hair cells and/or neural elements in the sensory epithelium. In the mammalian cochlea, this efferent system originates in the superior olivary complex and has been called the olivocochlear (OC) pathway and consists of a medial (MOC) and lateral (LOC) component. Cochlear efferent is likely to serve two functions: protection from acoustic over stimulation and enhancement of sound recognition in the presence of background noises. In the last project period, we determined that the MOC efferent could protect the cochlea from acoustic over stimulation working through the newly discovered alpha 9/10 nACh receptor complex. In this next project period, we will focus on the LOC efferent fibers that contain calcitonin gene-related peptide (CGRP). We determined that the loss of CGRP in knockout mice reduced sound-evoked activity of the cochlear nerve, which would then cause a reduction in the dynamic range of sound perception. However there are several CGRP-ergic neuronal systems in hair cell organs: the efferent as well as pathways innervating the vasculature, which could have contributed to the auditory phenotype. Our goal is to determine the molecular mechanism by which CGRP released from efferent fibers influences neuronal afferents. In these aims we will (1) determine effect of CGRP receptor signaling on sound-evoked activity; (2) determine biochemical time course for CGRP receptor signaling; (3) determine physiological target cells for CGRP receptor signaling. We will use adenoviral gene transfer, DPOAE, ABR, and CAP testing for auditory function, immunohistochemisty, coimmunoprecipitation, biolistic transfection, and FRET imaging to carry out these aims. Information gained from these studies will provide direct assessment of the molecular mechanisms used by the CGRP efferent feedback pathway to enhance sound-evoked activity in the cochlear nerve.