Influence of Age on Vestibular Sympathetic Reflexes

说明(申请人摘要)：在人类中，年龄与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的增加有关。与年龄相关的直立性低血压增加的一个机制可能是前庭交感神经反射的减弱。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来调节交感神经流出。目前还没有数据可以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说：1)肌交感神经活动(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相互作用过程中，MSNA的调制随着年龄的增长而改变。为了达到这些目的，将对一组年轻和老年受试者在耳石器官刺激(头下颈屈曲)前后进行MSNA测量(显微神经学检查)。此外，还将在心血管反射激活(肌肉传入、压力感受性反射激活和立位激发)过程中测量前庭-交感反射反应。这些研究的结果将提供关于老年人前庭交感反射的功能和重要性的新的临床重要信息。

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.