CELL INTERACTIONS IN THE DEVELOPING AUDITORY SYSTEM

发育中的听觉系统中的细胞相互作用

基本信息

批准号：
3215856
负责人：
THOMAS N PARKS
金额：
$ 27.49万
依托单位：
UNIVERSITY OF UTAH
依托单位国家：
美国
项目类别：
财政年份：
1979
资助国家：
美国
起止时间：
1979-03-01 至 2000-08-31
项目状态：
已结题

项目摘要

This research project is directed at understanding how interactions between functionally-linked nerve cells influence development of the specialized neuronal forms and functions found in the brainstem auditory system of mammals and birds. The first group of experiments will investigate how the forms of the highly-specialized axon terminals and synapses found in the cochlear nucleus are influenced by interaction of developing axons with their target neurons. Previous findings from this project have suggested that some neurons (e.g., in the cochlear ganglion) have more potential than others (e.g., in the cochlear nucleus) to form a diversity of axon terminal types under the control of different target neurons. This hypothesis will be evaluated experimentally in chick embryos by pairing abnormal synaptic partners through in vivo transplantations and through in vitro co-cultures of brainstem neurons with various ganglion neurons; the structures of the resulting axon terminals and synapses would be studied by light and electron microscopy. During development, the neurotransmitter amino acids glutamate and gamma- aminobutyric acid (GABA) can produce large changes in cytosolic free calcium concentrations ([Ca2+]i) in neurons; these changes in turn can affect a variety of developmental processes, including growth of axons and dendrites, synapse formation, and cell death. Glutamate is the principal excitatory neurotransmitter in the brainstem auditory system of birds and mammals and GABAergic endings are also prevalent there. In the developing brain stem auditory nuclei of the chick, changes in glutamate and GABA receptors have recently been found to occur in parallel with morphological transformations that give these neurons characteristic shapes related to their functions in hearing; this has suggested that amino acid receptor-induced changes in [Ca2+]i could underlie these events. A second group of proposed experiments is therefore directed at understanding how 1) normal maturation of receptor structure and function affects changes in [Ca2+]i evoked by glutamate and GABA and 2) how normal maturation of these receptors is affected by altered levels of stimulation, including those that occur after early deafening. These studies would make use of immunohistochemical and in situ hybridization histochemical localization of receptor proteins and messenger RNAs, cobalt sulfide histochemical localization of agonist- induced calcium accumulation, quantitative fluorescence microscopy of evoked changes in [Ca2+]i, and whole-cell patch-clamp electrophysiological analysis of the permeability of various receptor- associated channels to Ca2+. These studies will 1) contribute to further development of an animal model of congenital hearing loss that has been widely used for studies of development and regeneration in the auditory system and 2) explore the ability of various sensory ganglion neurons to successfully innervate central auditory neurons.

该研究项目旨在了解互动方式在功能连接的神经细胞之间会影响在脑干听觉中发现的专门神经元形式和功能哺乳动物和鸟类的系统。第一组实验将调查高度特殊的轴突终端的形式和在人工耳蜗核中发现的突触受到相互作用的影响用其靶神经元开发轴突。以前的发现项目建议一些神经元（例如，在人工耳蜗中）比其他人具有更大的潜力（例如，在人工耳蜗中）在不同目标控制下的轴突终端类型多样性神经元。该假设将在雏鸡中进行实验评估通过在体内配对异常突触伴侣来配对异常的胚胎移植和通过体外共同培养脑干神经元有各种神经节神经元；产生的轴突的结构末端和突触将通过光和电子显微镜研究。在发育过程中，神经递质氨基酸谷氨酸和γ- 氨基丁酸（GABA）可以产生巨大的变化胞质的变化神经元中的钙浓度（[Ca2+] i）；这些变化依次可以影响各种发育过程，包括轴突的生长和树突，突触形成和细胞死亡。谷氨酸是脑干听觉系统中的主要兴奋性神经递质鸟类和哺乳动物以及加巴能的结局也很普遍。在雏鸡发育中的脑干听觉核的变化最近发现谷氨酸和GABA受体发生在与形态转化相似，使这些神经元具有特征形状与它们在听力方面的功能相关；这就是建议氨基酸受体诱导的[Ca2+] i的变化可以这些事件是基础。第二组提出的实验是因此旨在了解1）受体正常成熟结构和功能会影响[Ca2+]的变化，我被谷氨酸诱发和 GABA和2）这些受体的正常成熟如何受到刺激水平的改变，包括早期发生的刺激震耳欲聋。这些研究将利用免疫组织化学和受体蛋白和原位杂交组织化学定位 Messenger RNA，激动剂的硫化钴组织化学定位诱导的钙积累，定量荧光显微镜诱发[Ca2+] I和全细胞贴片钳的变化电生理分析各种受体的渗透性相关的通道到Ca2+。这些研究将1）有助于进一步发展动物先天性听力损失的模型已被广泛用于研究听觉系统中的发展和再生以及2）探索各种感觉神经节神经元成功支配的能力中央听觉神经元。