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的连接形成和功能活动中发挥关键作用。然而，这还没有在耳石器时代的路径上得到证明，因为没有简单的方法来剥夺地球上的引力刺激系统。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。在这里，我们将进行地面研究，这将是我们未来太空飞行实验的控制。在这项工作中，将研究一种简单而已建立的鸟类模型，即雏鸡切线前庭核。这个核团的主要细胞是二级前庭神经元，参与协调头部和眼睛运动的三个神经元的前庭-眼反射和前庭小球反射。这个实验室有很长的历史，进行结构/功能的组合研究，以研究已确定的老年鸡胚胎和孵化的前庭核神经元的神经元兴奋性。对主细胞发育的了解比任何其他类型的前庭核神经元都要多。然而，几乎没有关于它们最早的功能发育以及微重力如何影响它们的研究。这些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的定量分析，以及在鸡胚胎(E5-E12)和完整孵化的雏鸡的脑片上注射低分子示踪剂。具体目标包括：(1)描述雏鸡前庭核内耳石器传入形成的通路、分布和终末及其与壶腹神经输入的关系；(2)研究去极化电流脉冲反应动作电位产生的开始和出现，并确定潜在的膜电导，重点是钾通道；(3)研究缝隙连接介导的前庭神经元和神经胶质细胞之间的细胞间通讯；(4)确定形成切向核(前庭外侧核)第一批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).