Mechanisms of Aging in the Somatosensory System

该应用程序结合了三个既定的专业知识 感官生物学实验室，研究细胞，分子和 生理方面的年龄相关的变化，在躯体感觉系统。的 实验解决了计划公告（99-123）的目标，标题为 老化的感觉：多个感觉系统之间的关系。远景目标 这项研究的目的是确定导致 感觉神经元及其终末器官的变性，并确定是否 调节由皮肤提供的营养支持水平可以减轻 与年龄相关的感觉缺陷的发生和进展。的感觉 触觉、疼痛和温度是通过各种形态和 位于皮肤中的电生理学上不同的机械感觉末梢。 这些末梢由感觉神经元和专门的终末器官组成， 例如，在一个实施例中，默克尔复合体，迈斯纳小体，经历变性， 老化的后果。神经支配的丧失会导致触觉 可能对工作绩效和质量产生重大影响的敏感性 对于老年人来说。研究表明，PNS的萎缩是 其特征在于神经元敏感性降低， 和/或外围终端的数量。我们假设这些退化的 变化与生长因子信号传导有关，特别是对于 神经营养因子NT 3和BDNF。过表达NT 3或NT 4的转基因小鼠的研究 皮肤中的BDNF已经表明它们以非常特定的方式起作用， 感觉末梢的发育、维持和生理特性。在这 项目我们建议确定NT 3和BDNF如何影响形态， 感觉神经元的细胞和生理特性， 皮肤/神经/脊髓制备。该制剂将用于鉴定 皮肤神经元的生理特性和化学表型 年轻和年老的小鼠以及在皮肤中过度表达NT 3或BDNF的小鼠。在 这样，我们将定义灵敏度和响应特性的差异， 与神经元表型和年龄的关系，并确定营养因子如何改变 这些财产。为了探索为什么神经元在衰老系统中失去敏感性， 我们将分析通道受体蛋白的表达，这些蛋白被认为是介导 青年和老年小鼠生理特征神经元的机械感觉 并确定它们的表达是否响应于海拔的升高而被调节， NT 3或BDNF表达。实验设计将使用免疫细胞化学， 免疫印迹、RT-PCR和原位杂交分析RNA和蛋白质 表达，用于生理学的离体皮肤/神经/脊髓制备， 分析和组成型或诱导型表达的转基因小鼠 皮肤中NT 3 nr BDMF的水平增加。

This application combines the expertise of three established laboratories in sensory biology to investigate the cellular, molecular and physiological aspects of age-related changes in the somatosensory system. The experiments address the goals of the Program Announcement (99-123) titled The Aging Senses: Relationships Among Multiple Sensory Systems. The long-term goal of this research is to identify the cellular mechanisms that lead to degeneration of sensory neurons and their end organs and determine whether modulating the level of trophic support provided by the skin can alleviate the onset and progression of age-related deficits in sensation. Sensations of touch, pain and temperature are transmitted by a variety of morphologically and electrophysiologically distinct mechanosensory endings located in the skin. These endings are comprised of sensory neurons and specialized end organs, e.g., Merkel complexes, Meissner corpuscles, that undergo degeneration as a consequence of aging. The loss of innervation causes reduced tactile sensitivity that can have significant impact on job performance and the quality of life for elderly individuals. Studies have shown that atrophy in the PNS is characterized by decreased neuron sensitivity and reduction in the integrity and/or number of peripheral terminals. We hypothesize these degenerative changes are related to growth factor signaling, in particular for the neurotrophins NT3 and BDNF. Studies of transgenic mice that overexpress NT3 or BDNF in the skin have shown they act in very specific manners to enhance sensory ending development, maintenance and physiological properties. In this project we propose to identify how NT3 and BDNF affect the morphological, cellular and physiological properties of sensory neurons using an ex vivo skin/nerve/spinal cord preparation. This preparation will be used to identify the physiological properties and chemical phenotype of cutaneous neurons of young and old mice and mice that overexpress either NT3 or BDNF in the skin. In this way we will define differences in sensitivity and response properties in relation to neuron phenotype and age, and determine how trophic factors alter these properties. To explore why neurons lose sensitivity in the aging system, we will analyze the expression of channel receptor proteins thought to mediate mechanosensation in physiologically characterized neurons of young and old mice and determine whether their expression is modulated in response to elevation in NT3 or BDNF expression. The experimental design will use immunocytochemistry, immunoblotting, RT-PCR and in situ hybridization to analyze RNA and protein expression, an ex vivo skin/nerve/spinal cord preparation for physiological analysis and transgenic mice that either constitutively or inducibly express increased levels of NT3 nr BDMF in the skin.