Nosikova Inna, Riabova Alexandra, Amirova Liubov, Kitov Vladimir, Tomilovskaya Elena
Laboratory of Gravitational Physiology of the Sensorimotor System, Institute of Biomedical Problems of Russian Academy of Science, Moscow, Russia.
Front Hum Neurosci. 2021 Dec 1;15:753259. doi: 10.3389/fnhum.2021.753259. eCollection 2021.
As female astronauts participate in space flight more and more frequently, there is a demand for research on how the female body adapts to the microgravity environment. In particular, there is very little research on how the neuromuscular system reacts to gravitational unloading in women. We aimed to estimate changes in motor evoked potentials (MEPs) in the lower leg muscles in women after 3-day exposure to Dry Immersion (DI), which is one of the most widely used ground models of microgravity. Six healthy female volunteers (mean age 30.17 ± 5.5 years) with a natural menstrual cycle participated in this experiment. MEPs were recorded from the gastrocnemius and soleus muscles twice before DI, on the day of DI completion, and 3 days after DI, during the recovery period. To evoke motor responses, transcranial and trans-spinal magnetic stimulation was applied. We showed that changes in MEP characteristics after DI exposure were different depending on the stimulation site, but were similar for both muscles. For trans-spinal stimulation, MEP thresholds decreased compared to baseline values, and amplitudes, on the contrary, increased, resembling the phenomenon of hypogravitational hyperreflexia. This finding is in line with data observed in other experiments on both male and female participants. MEPs to transcranial stimulation had an opposing dynamic, which may have resulted from the small group size and large inter-subject variability, or from hormonal fluctuations during the menstrual cycle. Central motor conduction time remained unchanged, suggesting that pyramidal tract conductibility was not affected by DI exposure. More research is needed to explore the underlying mechanisms.
随着女性宇航员越来越频繁地参与太空飞行，对女性身体如何适应微重力环境的研究需求也随之而来。特别是，关于女性神经肌肉系统对重力卸载的反应的研究非常少。我们旨在评估女性在经历3天的干浸（DI）后小腿肌肉运动诱发电位（MEP）的变化，干浸是最广泛使用的微重力地面模型之一。六名具有自然月经周期的健康女性志愿者（平均年龄30.17±5.5岁）参与了本实验。在干浸前、干浸完成当天以及干浸后3天的恢复期，从腓肠肌和比目鱼肌记录两次MEP。为了诱发运动反应，采用了经颅和经脊髓磁刺激。我们发现，干浸暴露后MEP特征的变化因刺激部位而异，但两块肌肉的变化相似。对于经脊髓刺激，与基线值相比，MEP阈值降低，而幅度则相反增加，类似于低重力性反射亢进现象。这一发现与在其他针对男性和女性参与者的实验中观察到的数据一致。经颅刺激的MEP有相反的变化趋势，这可能是由于样本量小和个体间差异大，或者是由于月经周期中的激素波动所致。中枢运动传导时间保持不变，表明锥体束传导性不受干浸暴露的影响。需要更多的研究来探索其潜在机制。
