Impact of a simulated gravity load for atmospheric reentry, 10 g for 2 min, on conscious mice
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The Japan Aerospace Exploration Agency recently performed a mouse experiment in the International Space Station in which mice were raised for 35 days, retrieved using the Dragon spacecraft, and then harvested for analysis 2 days after splashdown. However, the impact of the retrieval procedure, which exposed mice to 5–10 g for 2 min during atmospheric reentry and splashdown, was unknown. Therefore, the purpose of this study was to examine the impact of a 10 g load for 2 min (using a gondola-type centrifuge with a 1.5-m arm installed at Gifu University) on conscious mice. Plasma corticosterone increased at 30 min after load application and recovered at 90 min. Significant Fos expression was observed in the vestibular nuclei (VeN), paraventricular hypothalamic nucleus (PVN), and central nucleus of the amygdala (CeA). Rearing behavior and food intake were suppressed. Mice with vestibular lesions demonstrated increased corticosterone and Fos expression in the PVN, but neither suppression of food intake and rearing behavior nor increased Fos expression in the VeN and CeA. These results suggest that the simulated gravity load induced a transient stress response, hypoactivity, and a vestibular-mediated suppression of food intake.
KeywordsHypergravity Atmospheric reentry Fos Corticosterone Vestibular lesion
H.M., D.S., M.S., and S.T. were involved in the conception and design of the experiments. H.M. and A.Y. performed the experiments and were involved in collection, analysis, and interpretation of the data. H.M. wrote the manuscript and prepared all figures. All authors reviewed the manuscript and approved the final version. All persons designated as authors qualify for authorship, and all those who qualify for authorship are listed.
Compliance with ethical standards
Sources of funding
This study was supported by the short arm centrifuge project, commissioned from Japan Aerospace Exploration Agency (15YPTK-002009), and prioritized research selected for life science from Japan Aerospace Exploration Agency (14YPTK-005512). HM received support from the Japan Ministry of Education, Culture, Sports, Science and Technology via a Grant-in-Aid for Scientific Research on Innovative Areas (grant number 15H05935, “Living in Space”) and a Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science (15K11916). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Conflict of interest
The authors have no conflicts of interest to declare.
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