Yates B J, Kerman I A
Department of Otolaryngology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Brain Res Brain Res Rev. 1998 Nov;28(1-2):73-82. doi: 10.1016/s0165-0173(98)00028-9.
Even after short spaceflights, most astronauts experience at least some postflight reduction of orthostatic tolerance; this problem is severe in some subjects. The mechanisms leading to postflight orthostatic intolerance are not well-established, but have traditionally been thought to include the following: changes in leg hemodynamics, alterations in baroreceptor reflex gain, decreases in exercise tolerance and aerobic fitness, hypovolemia, and altered sensitivity of beta-adrenergic receptors in the periphery. Recent studies have demonstrated that signals from vestibular otolith organs play an important role in regulating blood pressure during changes in posture in a 1-g environment. Because spaceflight results in plastic changes in the vestibular otolith organs and in the processing of inputs from otolith receptors, it is possible that another contributing factor to postflight orthostatic hypotension is alterations in the gain of vestibular influences on cardiovascular control. Preliminary data support this hypothesis, although controlled studies will be required to determine the relationship between changes in the vestibular system and orthostatic hypotension following exposure to microgravity.
即使是短时间的太空飞行后，大多数宇航员至少会经历一些飞行后立位耐力的下降；这个问题在一些受试者中很严重。导致飞行后体位性不耐受的机制尚未完全明确，但传统上认为包括以下几点：腿部血液动力学变化、压力感受器反射增益改变、运动耐力和有氧适能下降、血容量减少以及外周β-肾上腺素能受体敏感性改变。最近的研究表明，在1g环境中姿势改变期间，来自前庭耳石器官的信号在调节血压方面起着重要作用。由于太空飞行会导致前庭耳石器官以及耳石感受器输入处理过程发生可塑性变化，所以飞行后体位性低血压的另一个促成因素可能是前庭对心血管控制的影响增益改变。初步数据支持这一假设，不过还需要进行对照研究来确定暴露于微重力环境后前庭系统变化与体位性低血压之间的关系。
