Cellular Mechanisms of the Vestibular System

描述（由申请人提供）：这是对前庭器官中突触传递的持续研究，重点是I型毛细胞及其花萼末端，仅在爬行动物、鸟类和哺乳动物中发现的遗传学上的最新收购。这些结构仅限于爬行动物和鸟类的中央/纹状体区。它们在哺乳动物中的重要性日益增加，这是因为它们分布在所有器官的神经上皮中。此外，虽然I型和II型毛细胞在啮齿动物嵴中的数量大致相等，但I型毛细胞在猴子和可能的人类嵴中占主导地位。这些结构的特殊结构和独特的生理学提出了关于突触传递如何完成的问题。1)I型毛细胞具有独特的基底外侧电流，可能会损害突触传递; 2）管家功能不能由支持细胞完成; 3）萼末端的几何形状和电生理学对突触电流流向尖峰编码器提出了不寻常的要求。关于这些问题是如何解决的，我们只有一些零碎的知识.然而，由于这些结构在哺乳动物（包括人类）中变得越来越重要，这些知识对于我们理解前庭器官如何处理信息至关重要。在临床上，I型毛细胞和/或其萼末端对氨基糖苷类耳毒性和年龄相关性退化特别敏感。将在海龟后嵴进行生理学研究，并将与在大鼠和海龟中进行的形态学研究相结合。有三个具体目标。1)毛细胞：我们将通过从花萼末端进行全细胞记录来表征I型毛细胞的突触传递。该假说认为，在低频前庭毛细胞中，I型毛发的神经递质释放可能不同于高频听觉和振动器官。2)稳态：在转导过程中，K+离子和谷氨酸神经递质都从毛细胞释放。在II型毛细胞的情况下，支持细胞用于清除这些物质。萼末端的存在排除了支持细胞以与I型毛细胞相同的方式起作用。我们假设，I型毛细胞和/或其结束suburbs这些管家功能。3)突触后机制：我们将探讨各种离子通道和神经递质受体如何塑造突触和尖峰活动。有待检验的假设是，花萼的分子组织产生了具有离散功能的独立微区：突触传递、尖峰起始和放电规律。

DESCRIPTION (provided by applicant): This is a continuing study of synaptic transmission in vestibular organs with emphasis on the type I hair cell and its calyx ending, phylogenetically recent acquisitions only found in reptiles, birds and mammals. These structures are restricted to central/striolar zones in reptiles and birds. Their increasing importance in mammals is suggested by their distribution throughout the neuroepithelium of all organs. In addition, while type I and type II hair cells occur in approximately equal numbers in rodent cristae, type I hair cells predominate in the cristae of monkeys and possibly of humans. The peculiar structure and distinctive physiology of these structures raise problems as to how synaptic transmission is accomplished. 1) Type I hair cells have a distinctive basolateral current that may compromise synaptic transmission; 2) Housekeeping functions cannot be done by supporting cells; and 3) The geometry and electrophysiology of the calyx ending place unusual demands on the flow of synaptic currents to the spike encoder. We have only fragmentary knowledge as to how these problems are solved. Yet, because these structures become of increasing importance in mammals (including humans), such knowledge is crucial to our understanding as to how vestibular organs process information. Of clinical interest, the type I hair cell and/or its calyx ending are especially sensitive to aminoglycoside ototoxicity and age-related degeneration. Physiological studies will be done in the turtle posterior crista and will be integrated with morphological studies to be done in rats and turtles. There are three specific aims. 1) Hair cells: We will characterize synaptic transmission from type I hair cells by making whole- cell recordings from the calyx ending. The hypothesis is that neurotransmitter release from type I hair in low- frequency vestibular hair cells may differ from high-frequency auditory and vibratory organs. 2) Homeostasis: Both K+ ions and glutamate neurotransmitter are released from hair cells during transduction. In the case of type II hair cells, supporting cells serve to clear these substances. The presence of the calyx ending precludes supporting cells from acting in the same way for type I hair cells. We hypothesize that the type I hair cell and/or its ending subsume these housekeeping functions. 3) Postsynaptic mechanisms: We will explore how various ion channels and neurotransmitter receptors shape synaptic and spiking activity. The hypothesis to be tested is that the molecular organization of the calyx creates separate microdomains with discrete functions: synaptic transmission, spike initiation, and discharge regularity.