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相互作用如何功能相连的神经细胞之间影响发育脑干听觉中发现的特殊神经元形式和功能哺乳动物和鸟类的系统。第一组实验将研究高度专业化的轴突末端的形式和耳蜗核中发现的突触受到相互作用的影响与目标神经元一起发育轴突。之前的发现项目表明一些神经元（例如，在耳蜗神经节中）比其他（例如，在耳蜗核中）更有潜力形成不同目标控制下的多种轴突末端类型神经元。该假设将在小鸡身上进行实验评估通过体内配对异常突触伙伴来胚胎脑干神经元移植和体外共培养与各种神经节神经元；由此产生的轴突的结构末端和突触将通过光学和电子显微镜进行研究。在发育过程中，神经递质氨基酸谷氨酸和γ- 氨基丁酸（GABA）可以使胞质游离产生较大变化神经元中的钙浓度 ([Ca2+]i)；这些变化反过来又可以影响多种发育过程，包括轴突的生长以及树突、突触形成和细胞死亡。谷氨酸是脑干听觉系统中主要的兴奋性神经递质鸟类和哺乳动物的基因和 GABA 能结局在那里也很普遍。在雏鸡脑干听觉核团的发育过程中，最近发现谷氨酸和 GABA 受体存在于与给予这些神经元的形态转变平行与其听觉功能相关的特征形状；这有表明氨基酸受体诱导的 [Ca2+]i 变化可以这些事件的背后。第二组提议的实验是因此旨在了解 1) 受体的正常成熟结构和功能影响谷氨酸引起的 [Ca2+]i 变化 GABA 和 2) 这些受体的正常成熟如何受到影响刺激水平的改变，包括早期发生的刺激水平震耳欲聋。这些研究将利用免疫组织化学方法受体蛋白的原位杂交组织化学定位信使 RNA、激动剂的硫化钴组织化学定位诱导钙积累，定量荧光显微镜引起 [Ca2+]i 和全细胞膜片钳变化各种受体通透性的电生理分析 Ca2+ 的相关通道。这些研究将 1) 有助于动物的进一步发育已广泛用于研究的先天性听力损失模型听觉系统的发育和再生，2）探索各种感觉神经节神经元成功神经支配的能力中枢听觉神经元。