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Interpretation of the mechanism of cardiovascular deconditioning induced by the long-term exposure to microgravity.

解释长期暴露于微重力引起的心血管失调的机制。

基本信息

批准号：
07045048
负责人：
MANO Tadaaki
金额：
$ 3.07万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07045048/
关键词：
muscle sympathetic nerve activity cardiovascular deconditioning microgravity bed rest dry immersion static exerc orthostatic stress 微小神経電図法ヘッドアップティルト心拍変動血圧変動 -6ﾟヘッドダウンティルト dry immersion 血管迷走神経性失神

项目摘要

On return to the earth sfter spaceflight, cardiovascular deconditioning, including fall in blood pressure and sometimes syncope, is known to occur. Variable autonomic symptons were reported during spaceflight. However, the effect of microgravity on autonomic function is almostly unclear. We performed 3 days of dry immersion (DI) as the stimulation of short duration microgravity and 120 days of 6-degree head-down bed rest (BR) as that of long duration weightlessness.After 3 days of DI,resting muscle sympathetic nerve activity (MSNA) recorded with use of microneurography, and resting cardiac sympathetic nerve activity indicated by heart rate variability were higher than those before DI,and resting cardiac vagal activity was lower than that before DI.Systolic and diastolic blood pressure werre similar to that before DI.Increasing response of MSNA,cardiac sympathetic nerve activity and heart rate to orthostatic stress, and decreasing response of cardiac vagal activity to it were maintained. After 12 _o days of BR,resting MSNA and heart rate were higher than those before BR.Systolic and diastolic blood pressure werre similar to that before BR.Rises in MSNA and heart rate in response to orthostatic stress were maintained. Systolic and diastolic blood pressure resposes to it did not change. However, increasing response in MSNA to static leg exercise (30% maximal voluntary contraction) was declined and rise in mean blood pressure to it disappeared. 3 days of the exposure to microgravity and 120 days of it increased MSNA to almost same degree. From the assessment of changes in MSNA,heart rate (variability) and blood pressure, both of them did not effect autonomic responses to orthostatic stress, but the latter declined the MSNA response.

众所周知，太空飞行后返回地球时，会发生心血管失调，包括血压下降，有时甚至晕厥。据报道，在航天飞行期间出现了各种自主神经症状。然而，微重力对自主神经功能的影响几乎还不清楚。以3天的干浸（DI）作为短期失重刺激，120天的头低位卧床（BR）作为长期失重刺激，DI后3天，显微神经电图记录的静息肌交感神经活动（MSNA）和心率变异性（HRV）显示的静息心交感神经活动均高于DI前，静息时心脏迷走神经活动较DI前降低，收缩压和舒张压与DI前相似，MSNA、心脏交感神经活动和心率对立位应激反应增强，而心脏迷走神经活动反应减弱。BR后12天，静息MSNA和心率较BR前升高，收缩压和舒张压与BR前相似，立位应激时MSNA和心率的升高得以维持。收缩压和舒张压无明显变化。然而，MSNA对静态腿部运动（30%最大自主收缩）的反应增加下降，平均血压升高消失。暴露于微重力3天和120天使MSNA增加到几乎相同的程度。从MSNA，心率（变异性）和血压的变化评估，他们都没有影响自主反应直立应激，但后者下降MSNA反应。