Nicotinic Receptors in Cochlear Hair Cell Physiology

耳蜗毛细胞生理学中的烟碱受体

• 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
• 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
• 来源: https://reporter.nih.gov/project-details/6888536
• 关键词: RNase protection assay; South America; Xenopus oocyte; acetylcholine; cochlea; computer program /software; ear hair cell; efferent nerve; electrophysiology; embryonic stem cell; gene targeting; genetically modified animals; in situ hybridization; innervation; laboratory mouse; laboratory rat; molecular cloning; neuropharmacology; neurotransmitter agonist; neurotransmitter antagonist; nicotinic receptors; protein structure function; receptor expression; synapses; voltage /patch clamp; voltage gated channel

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，特别是分子遗传学的出现，以探索听力损失的潜在机制。据估计，每1 000名新生儿中就有1人严重失聪，而每20名新生儿中就有近1人有严重的听力障碍。在这些病例中，一半以上的原因是遗传性的。截至2002年2月，29个特定基因与不同形式的非综合征性人类耳聋有关。此外，许多其他基因产物参与正常耳蜗功能已被确定。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（α 9和α 10）。α 9和α 10编码受体蛋白，其介导传出神经元释放的乙酰胆碱（ACh）对耳蜗毛细胞的作用。主要研究者（Fuchs）表明，钙通过ACh受体进入导致毛细胞超极化，减少递质释放，导致听觉神经纤维的调谐和敏感性丧失。该FIRCA提案汇集了Fuchs和Elgoyhen实验室的专业知识，进行了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。这项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的作用，在响亮的声音或耳毒性药物产生的听力障碍的成因和潜在的治疗。本申请的直接目的有三个方面：首先，在急性耳蜗外植体中，在非洲爪蟾卵母细胞中表达的重组α 9/α 10受体与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，内毛细胞中胆碱能反应的个体发生的表征，第三，在Acra 9基因中具有遗传修饰的小鼠，即α 9无效突变小鼠和携带功能获得突变的敲入小鼠中，对突触接触到内毛细胞和外毛细胞上的生理学分析。这项研究将主要在阿根廷的INGEBI（国家研究理事会）与Ana Belen Elgoyhen合作完成，作为NIH资助#R01 DC 01508的延伸。