Influence of Age on Vestibular Sympathetic Reflexes

描述（申请人摘要）：衰老与人类直立性低血压的发生率增加有关。直立性低血压已被证明与死亡率增加有关。一种机制可能负责与年龄相关的直立性低血压增加是前庭交感反射的衰减。这种反射是一种神经反馈系统，通过前庭耳石器官的传入输入调节交感神经流出。目前尚无数据确定年龄对这种反射的影响。因此，本研究的主要目的是验证两个假设：1)肌肉交感神经活动（MSNA）对耳石器官刺激的反应随着年龄的增长而减弱；2)在前庭交感神经反射与其他心血管反射的相互作用中，MSNA的调节随着年龄的增长而改变。为了实现这些目标，将在一组年轻和老年受试者耳石器官刺激（头部向下颈部弯曲）前后测量MSNA（微神经造影）。此外，在心血管反射激活（肌肉传入、压力反射激活和直立挑战）期间，将测量前庭交感反射反应。这些研究的结果将提供新的和临床重要的信息关于前庭交感神经反射的功能和重要性在老年人。

DESCRIPTION (Applicant's abstract): Aging is associated with an increased incidence of orthostatic hypotension in humans. Orthostatic hypotension has been shown to be associated with increased mortality. One mechanism that may be responsible for the age-related increases in orthostatic hypotension is attenuation of the vestibulo-sympathetic reflex. This reflex is a neural feedback system that regulates sympathetic neural outflow via afferent input from the vestibular otolith organs. Currently no data exist determining the influence of age on this reflex. Accordingly, the Primary aim of the present proposal is to test two hypotheses: 1) muscle sympathetic nerve activity (MSNA) responses to otolith organ stimulation are attenuated with aging; and 2) modulation of MSNA during the interaction between the vestibulo-sympathetic reflex and other cardiovascular reflexes is altered with aging. To address these aims, MSNA will be measured (microneurography) in a group of young and older subjects before and after otolith organ stimulation (head down neck flexion). Additionally, the vestibulo-sympathetic reflex responses will be measured during cardiovascular reflex activation (muscle afferents, baroreflex activation, and orthostatic challenge). The results of these studies will provide new and clinically important information concerning the function and importance of the vestibulo-sympathetic reflex in aging adult humans.