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，以及在这个微重力周期前后1.5到2.0G的超重力。使用显微神经学技术记录坐在乘客座位上的健康人的二叉神经的肌肉交感神经活动(MSNA)。我们使用了名古屋国际机场旁边的钻石航空服务公司的MU-300(三菱重工)喷射机。用钨微电极记录支配小腿三头肌的MSNA，同时用Finapres记录心电图、呼吸曲线、血压波形、胸腔内血容量、自然呼吸和控制(0.25 Hz)呼吸的心阻抗图。MSNA在超重力条件下被激活(177%)，在微重力条件下被抑制(52%)，在自然呼吸条件下，这种激活和抑制是短暂的和阶段性的。在微重力的后半期，MSNA被激活，这是通过动脉压力感受器反射诱导的。这种激活-抑制序列在控制呼吸下减弱，可能是因为MSNA的控制机制可能从动脉压力反射占优势转变为心肺容量感受器占优势。

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.