DEVELOPMENT OF VESTIBULAR NUCLEI NEURONS

描述（由申请人提供）：在某些感觉系统中，天然感觉输入已被证明在CNS神经元的连接和功能活动的形成中起关键作用。然而，这一点尚未在耳石路径中得到证实，因为没有简单的方法可以剥夺地球上系统的重力刺激。因此，只有在空间飞行中才能研究微重力对中枢前庭发育的影响。在这里，我们将进行地面研究，这将是我们未来空间飞行实验的控制。本研究采用一种简单而成熟的禽类模型，鸡前庭神经切向核。该核的主要细胞是参与三神经元前庭-眼反射和前庭颈反射的二级前庭神经元，这些反射参与协调头部和眼睛的运动。本实验室有很长的历史，进行组合结构/功能的研究，以探讨神经元的兴奋性，在确定前庭核神经元的老年鸡胚和孵化。对主细胞发育的了解比对任何其他类别的前庭核神经元的了解都要多。然而，关于它们最早期的功能发育以及微重力如何影响这些功能发育的问题，却几乎没有定论。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，和低分子量示踪剂注射在鸡胚（E5-E12）和完整的孵化小鸡的脑切片。具体目标包括：（1）描述耳石传入在雏鸡前庭神经核中形成的通路、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引起的动作电位产生的起始和出现，并确定潜在的膜电导，重点是钾通道;（3）研究前庭神经元和神经胶质细胞之间缝隙连接介导的细胞间通讯;（4）确定在前庭外侧核（tangential nucleus，lateral vestibular nucleus）中形成第一个非前庭传入的轴突来源。

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).