DEVELOPMENT OF VESTIBULAR NUCLEI NEURONS

描述（由申请人提供）：在某些感觉系统中，自然感觉输入已被证明在中枢神经系统神经元连接和功能活动的形成中起着至关重要的作用。然而，由于没有简单的方法来剥夺地球上的引力刺激系统，这一点还没有在耳石途径中得到证实。因此，微重力对中央前庭发育的影响可以在太空飞行中进行独特的研究。我们将在这里进行地面研究，这将是我们未来太空飞行实验的控制。在这项工作中，我们将研究一个简单而成熟的鸟类模型——小鸡切向前庭核。该核的主要细胞是参与前庭-眼反射和前庭-丘反射的二级前庭神经元，它们参与协调头和眼的运动。该实验室长期以来一直在进行结构/功能联合研究，以研究已识别的老年小鸡胚胎和幼雏前庭核神经元的神经元兴奋性。我们对主细胞发育的了解比其他任何一类前庭核神经元都要多。然而，关于它们最早的功能发展，以及它如何受到微重力的影响，我们知之甚少。技术包括全细胞膜片钳记录、药理学测试、免疫细胞化学结合荧光共聚焦图像定量分析、低分子量示踪剂注射鸡胚胎（E5-E12）和完整孵化鸡脑切片。具体目的包括：(1)描述雏鸡前庭核耳石传入神经的通路、分布和终末，以及它们与幼雏壶腹神经输入的关系；(2)研究去极化电流脉冲下动作电位产生的开始和出现，识别潜在的膜电导，重点研究钾通道；(3)研究间隙连接介导的前庭神经元和神经胶质细胞间的细胞间通讯；(4)确定在切向核（外侧前庭核）中形成第一个非前庭输入的轴突的来源。

DESCRIPTION (provided by applicant): In certain sensory systems, natural sensory input has been to shown to play a crucial role in the formation of connections and functional activity of CNS neurons. However, this has not been demonstrated for the otolithic pathways since there is no simple way to deprive the system of gravitational stimulation on Earth. Thus, the effects of microgravity on central vestibular development can be studied uniquely in space flight. Here we will perform ground-based studies which will be the controls for our future space flight experiments. For this work, a simple and established avian model will be studied, the chick tangential vestibular nucleus. The principal cells of this nucleus are second-order vestibular neurons participating in the three-neuron vestibule-ocular and vestibulocollic reflexes, which are involved in coordinating head and eye movements. This laboratory has a long history performing combined structure/function studies to investigate neuronal excitability in identified vestibular nucleus neurons of older chick embryos and hatchlings. More is known about principal cell development than for any other class of vestibular nucleus neuron. However, little is established on their earliest functional development, and how it may be influenced by microgravity. The techniques include whole-cell patch clamp recording, pharmacological testing, immunocytochemistry combined with quantitative analysis of fluorescent confocal images, and low molecular weight tracer injections in brain slices of chick embryos (E5-E12) and intact hatching chicks. The specific aims include: (1) Describe the pathways, distribution, and terminals formed by otolithic afferents in the chick vestibular nuclei and their relationship to ampullary nerve inputs in hatchlings; (2) Study the onset and emergence of action potential generation in response to depolarizing current pulses and identify the underlying membrane conductance's, focusing on potassium channels; (3) Investigate gap-junction mediated intercellular communication among vestibular neurons and among glial cells; (4) Identify the source of axons forming the first non-vestibular inputs in the tangential nucleus (lateral vestibular nucleus).