Sympathoadrenal Activity in Humans During Spaceflight-2 (Sympatho-2)
Research Area: Nervous and Vestibular Systems
Expedition(s): 14, 19 -22, 25-ongoing
Principal Investigator(s): ● Niels J. Christensen, University of Copenhagen,
Copenhagen Denmark
RESEARCH OBJECTIVES
Sympathoadrenal Activity in Humans During Spaceflight-2 (Sympatho-2) studies the influence of
microgravity on adrenal activity in the sympathetic nervous system, which has importance for
cardiovascular system regulation such as accelerating heart rate, constricting blood vessels, and
raising blood pressure in long-duration space explorers. Ground-based experiments have shown
that the sympathetic activity is decreased in response to displacement of the blood from the lower
part of the body to the heart-lung area after changing from the upright or sitting position to the
supine (lying on back) position. In space, sympathetic activity is expected to be decreased but
experiments have suggested that it actually increases during weightlessness. This is the core
element of the Sympatho experiment
RESULTS
Eight male astronauts were studied between third and sixth
months of flight on the International Space Station. It was
observed that sympathetic nervous system activity but not
plasma epinephrine values were very high during the
mission and the level corresponded to values obtained in
sitting position on Earth. This response was most likely
related to the decrease observed in systemic vascular
resistance and arterial blood pressure observed during the
mission. The mechanism of the decrease in vascular
resistance during spaceflight has not been clarified, but it is
likely to be related to the blood and fluid shift to the upper
part of the body as observed during microgravity. Clearly a
high sympathetic nervous system activity is required for
astronauts to maintain an adequate blood pressure level in
space. Further studies of the mechanisms involved are
therefore of major importance.
This investigation is complete; however additional results are pending publication.
Centrifuge Plasma-03 to separate
blood into plasma and serum. ESA
image.