Microneurographic analy sis of muscle sympathetic nerve activity under microgravity induced by parabolic flight

抛物飞行器的抛物线飞行可以产生大约20秒的微重力，以及在微重力期间前后1.5至2.0 G的超重力。肌交感神经活动（MSNA）记录从双神经微神经摄影技术从健康的人坐在乘客座位。我们在名古屋国际机场附近使用了钻石航空公司附属的MU-300（三菱重工业）飞机。用钨微电极记录支配于肱三头肌表面的MSNA，同时记录心电图、呼吸曲线、Finapres血压波、自然呼吸和控制呼吸（0.25Hz）时阻抗心电图的胸内血容量。结果表明，MSNA在超重力条件下被激活（177%），在微重力条件下被抑制（52%），而这种激活和抑制在自然呼吸条件下是短暂的和相性的。在微重力后半期，通过动脉压力反射诱导MSNA活化。这种激活-抑制序列在呼吸控制下减弱，可能是由于MSNA的控制机制可能从以动脉压力反射为主转移到以心肺容量受体为主。

Parabolic flight by a ject aircraft can produce approximately 20 seconds of microgravity, and hypergravity of 1.5 to 2.0 G before and after this microgravity period. Muscle sympathetic nerve activity (MSNA) recorded from the bitial nerve using microneurographic technique from healthy humans sitting in a passenger seat. We used MU-300 (Mitsubishi Heavy Industries) ject aircraft affiliated to Diamond Air Service next to Nagoya International Airport. MSNA innervating to the triceps surae was recorded using tungsten microelectrode, simultaneously with electrocardiography, respiration curve, blood pressure wave with Finapres, intrathoracic blood volume with impedance cardiography with natural and controlled (0.25Hz) respiration. MSNA was revealed to be activated (177%) under hypergravity and suppressed (52%) under microgravity, and these activation and suppression were quite transient and phasic under natural respiration. During later half of microgravity period, MSNA was then activated, which was induced through arterial baroreflex. This activation-suppression series was attenuated under controlled respiration, probably because controlling mechanism of MSNA might transfer from arterial baroreflexdominant to cardiopulmonary volume receptor dominant.