Fritsch-Yelle J M, Charles J B, Jones M M, Beightol L A, Eckberg D L
Space Biomedical Research Institute, National Aeronautics and Space Administration Johnson Space Center, Houston, Texas 77058.
J Appl Physiol (1985). 1994 Oct;77(4):1776-83. doi: 10.1152/jappl.1994.77.4.1776.
Spaceflight is associated with decreased orthostatic tolerance after landing. Short-duration spaceflight (4-5 days) impairs one neural mechanism: the carotid baroreceptor-cardiac reflex. To understand the effects of longer-duration spaceflight on baroreflex function, we measured R-R interval power spectra, antecubital vein plasma catecholamine levels, carotid baroreceptor-cardiac reflex responses, responses to Valsalva maneuvers, and orthostatic tolerance in 16 astronauts before and after shuttle missions lasting 8-14 days. We found the following changes between preflight and landing day: 1) orthostatic tolerance decreased; 2) R-R interval spectral power in the 0.05 to 0.15-Hz band increased; 3) plasma norepinephrine and epinephrine levels increased; 4) the slope, range, and operational point of the carotid baroreceptor cardiac reflex response decreased; and 5) blood pressure and heart rate responses to Valsalva maneuvers were altered. Autonomic changes persisted for several days after landing. These results provide further evidence of functionally relevant reductions in parasympathetic and increases in sympathetic influences on arterial pressure control after spaceflight.
太空飞行与着陆后体位性耐力下降有关。短期太空飞行（4 - 5天）会损害一种神经机制：颈动脉压力感受器 - 心脏反射。为了解长期太空飞行对压力反射功能的影响，我们在16名宇航员执行8 - 14天的航天飞机任务前后，测量了他们的R - R间期功率谱、肘前静脉血浆儿茶酚胺水平、颈动脉压力感受器 - 心脏反射反应、对瓦尔萨尔瓦动作的反应以及体位性耐力。我们发现飞行前和着陆日之间有以下变化：1）体位性耐力下降；2）0.05至0.15赫兹频段的R - R间期频谱功率增加；3）血浆去甲肾上腺素和肾上腺素水平升高；4）颈动脉压力感受器心脏反射反应的斜率、范围和工作点降低；5）对瓦尔萨尔瓦动作的血压和心率反应发生改变。自主神经变化在着陆后持续了几天。这些结果进一步证明了太空飞行后副交感神经功能相关降低以及交感神经对动脉血压控制影响增加。
