Plastic alteration of vestibulo-cardiovascular reflex and its countermeasure (V-C REFLEX) - 11.22.16
In V-C Reflex, the vestibular system plays an important role in controlling arterial pressure upon posture change (vestibulo-cardiovascular reflex), although this system is highly plastic, i.e., the sensitivity of the vestibulo-cardiovascular reflex is altered if subjects are exposed to a different gravitational environment. Thus, it is possible that the sensitivity of vestibulo-cardiovascular reflex is diminished after spaceflight, and then orthostatic hypotension is induced. To test this hypothesis, the role of the vestibulo-cardiovascular reflex in maintaining arterial pressure upon posture change is examined before and after spaceflight.
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Hironobu Morita, Ph.D., M. D., Gifu University , Gifu, Japan
Yoshiharu Yamamoto, Ph.D, The University of Tokyo, Graduate School of Education, Bunkyo-ku, Tokyo , Japan
Kunihiko Tanaka, M.D., Ph.D., , Gifu University of Medical Science, Gifu, Japan
Chikara Abe, D.D.S., Ph.D., Gifu University Graduate School of Medicine, Seki , Japan
Space Environment Utilization Center, Japan Aerospace Exploration Agency, Tsukuba, Japan
Sponsoring Space Agency
Japan Aerospace Exploration Agency (JAXA)
Japan Aerospace Exploration Agency
ISS Expedition Duration
May 2012 - March 2016
- Orthostatic hypotension is one of the most common physical complications of spaceflight. One of the proposed mechanisms of this condition is the plastic alteration of the vestibulo-cardiovascular reflex, i.e., microgravity induces a plastic alteration of this reflex that may result in inadequate adjustment of the arterial pressure upon posture change. This possibility has to be examined in order to consider a prophylaxis and countermeasure of postflight orthostatic hypotension.
- The purpose of the research is to test the hypothesis that microgravity induces plastic alteration of the vestibulo-cardiovascular reflex, and vestibular-mediated pressor response is impaired after spaceflight, then orthostatic hypotension occurs. To examine this, contribution of the vestibulo-cardiovascular reflex in controlling AP upon head-up tilt (HUT) is examined before and after spaceflight.
- The vestibular system is known to be highly plastic; there are direct evidences of the altered vestibulo-ocular and vestibulo-spinal reflexes after spaceflight. However, a direct evidence of the altered vestibulo-cardiovascular reflex after spaceflight does not exist.
The objectives of the research are to test the hypothesis that vestibular-mediated pressure response is impaired after spaceflight, then orthostatic hypotension occurs. To examine this, contribution of the vestibulo-cardiovascular reflex in controlling arterial pressure upon HUT is examined before and after spaceflight. For transient interruption of the vestibular-mediated pressure response, galvanic vestibular stimulation (GVS) is applied. The HUT is performed with and without GVS. The contribution of vestibulo-cardiovascular reflex to arterial pressure maintenance during HUT is estimated by comparing the arterial pressure responses between GVS-on and GVS-off conditions.
This experiment has potential benefits to considering a prophylaxis and countermeasure of orthostatic hypotension in elderly subjects. Both spaceflight and elderly subjects whose daily activity is reduced, fluctuation of the vestibular input is low and both conditions are known to induce orthostatic hypotension. Thus, it is possible that the plastic alteration of the vestibulo-cardiovascular reflex is a relevant mechanism of orthostatic hypotension in these conditions.
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Morita H, Abe C, Tanaka K. Long-term exposure to microgravity impairs vestibulo-cardiovascular reflex. Scientific Reports. 2016 September 16; 6: 33405. DOI: 10.1038/srep33405. PMID: 27634181.
Ground Based Results Publications