Nicotinic Receptors in Cochlear Hair Cell Physiology

耳蜗毛细胞生理学中的烟碱受体

基本信息

批准号：
6888536
负责人：
Paul A Fuchs
金额：
$ 3.2万
依托单位：
JOHNS HOPKINS UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2003
资助国家：
美国
起止时间：
2003-04-01 至 2006-03-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant) Recent years have seen important developments in the study of hearing, especially the emergence of molecular genetics to probe the underlying mechanisms of hearing loss. It is estimated that 1 in every 1,000 newborns is profoundly deaf, while nearly 1 in 20 has a significant hearing impairment. In more than half of these cases, the cause is genetic. As of February 2002, twenty-nine specific genes have been associated with different forms of nonsyndromic human deafness. In addition, many other gene products involved in normal cochlear function have been identified. The foreign collaborator (Elgoyhen) cloned and characterized two novel nicotinic receptor genes (alpha 9 and alpha 10) that are expressed in cochlear hair cells. Alpha 9 and 10 encode receptor proteins that mediate the effect of acetylcholine (ACh) released by efferent neurons onto cochlear hair cells. The Principal Investigator (Fuchs) showed that calcium entry through the ACh receptor leads to hair cell hyperpolarization, reducing transmitter release to cause a loss of tuning and sensitivity in the auditory nerve fibers. This FIRCA proposal brings together the expertise of the Fuchs and Elgoyhen laboratories to conduct a series of electrophysiological and molecular genetic experiments to elucidate the properties and function of these cholinergic receptors in hair cell physiology. The long-term goal of this proposal is to define the physiological role of the hair cell's cholinergic receptor. In addition, it is expected that the results obtained will contribute to our understanding of the role of efferent cholinergic input in the genesis and potential treatment of hearing impairment produced by loud sound or ototoxic drugs. The immediate aims of this application are three-fold: first, the pharmacological and physiological comparison of recombinant alpha9/alpha10 receptors expressed in Xenopus laevis oocytes with native cholinergic receptors of inner and outer hair cells in acute cochlear explants; second, the characterization of the ontogeny of cholinergic responses in inner hair cells and third, the physiological analysis of synaptic contacts onto inner and outer hair cells in mice with genetic modifications in the Acra9 gene, namely the alpha9 null mutant mouse and a knock-in mouse bearing a gain of function mutation. This research will be done primarily in Argentina at INGEBI (National Research Council) in collaboration with Ana Belen Elgoyhen as an extension of NIH grant #R01 DC01508.

描述（由申请人提供）近年来，听力研究取得了重要进展，特别是用于探讨听力损失潜在机制的分子遗传学的出现。据估计，每 1,000 名新生儿中就有 1 人患有重度耳聋，而近二十分之一的新生儿有严重的听力障碍。在超过一半的病例中，原因是遗传的。截至 2002 年 2 月，已有 29 个特定基因与不同形式的非综合征性人类耳聋相关。此外，许多其他涉及正常耳蜗功能的基因产物也已被鉴定。国外合作者（Elgoyhen）克隆并鉴定了两种在耳蜗毛细胞中表达的新型烟碱受体基因（α9和α10）。 Alpha 9 和 10 编码受体蛋白，介导传出神经元释放的乙酰胆碱 (ACh) 对耳蜗毛细胞的影响。首席研究员 (Fuchs) 表明，钙通过 ACh 受体进入会导致毛细胞超极化，减少递质释放，导致听觉神经纤维失去调谐和敏感性。这项 FIRCA 提案汇集了 Fuchs 和 Elgoyhen 实验室的专业知识，进行一系列电生理学和分子遗传学实验，以阐明这些胆碱能受体在毛细胞生理学中的特性和功能。该提案的长期目标是确定毛细胞胆碱能受体的生理作用。此外，预计所获得的结果将有助于我们了解传出胆碱能输入在大声或耳毒性药物引起的听力损伤的发生和潜在治疗中的作用。该应用的直接目标有三个：首先，非洲爪蟾卵母细胞中表达的重组α9/α10受体与急性耳蜗外植体中内毛细胞和外毛细胞的天然胆碱能受体的药理学和生理学比较；第二，内毛细胞胆碱能反应的个体发育特征；第三，对 Acra9 基因进行遗传修饰的小鼠（即 alpha9 无效突变小鼠和敲入小鼠）内毛细胞和外毛细胞突触接触的生理学分析具有功能获得性突变的小鼠。这项研究将主要在阿根廷的 INGEBI（国家研究委员会）与 Ana Belen Elgoyhen 合作进行，作为 NIH 拨款 #R01 DC01508 的延伸。