not different between spaceflight and ground control mice. These results demonstrate that
spaceflight alters vasoconstrictor, mechanical, and gross structural properties of cerebral
resistance arteries. Collectively, these changes in the functional vasoconstrictor and mechanical
properties of cerebral arteries suggest that blood flow to the brain may be elevated during
spaceflight. Although elevated partial pressure of CO 2 in the closed microgravity environment
may contribute to alterations in the properties of cerebral arteries, high CO 2 levels alone cannot
fully account for such changes. Finally, if similar alterations in the properties of cerebral arteries
occur in crew members, elevations in brain blood flow could serve to elevate intracranial
pressure and possibly contribute to the visual impairment reported to occur in crew members
(Taylor 2013).
Cardiovascular adaptations to microgravity undermine the physiologic capacity to respond to
challenges related to an upright posture on return to terrestrial gravity. This study investigates
the influence of spaceflight on the constriction of mouse muscle arteries either in response to
a stimulus (vasoconstriction) or under their own power (myogenic contraction) and to
determine the impacts on bone and muscle mass loss. Total body mass tended to be lower in
spaceflight animals, and muscle mass was 7%-13% lower in spaceflight mice. Spaceflight was
found to decrease vasoconstrictor responses but did not affect the myogenic responsiveness.
The thickness of the vessel walls was not found to differ between the two groups. The lack of
change in vessel wall thickness suggests that the blood volume redistribution is insignificant in
mice during spaceflight and likely reflects that blood flow to the portion of muscle being tested
was preserved. This is an important shortcoming and demonstrates that the mouse may not be
an ideal animal model to study this phenomenon. If applicable to the human condition, these
results suggest that microgravity-induced changes in the vasoconstrictor characteristics of
skeletal muscle resistance arteries could compromise the ability to raise peripheral vascular
resistance in order to regulate arterial blood pressure when standing (Stabley 2012).
PUBLICATION(S)
Gridley DS, Mao XW, Tian J, et al. Genetic and apoptotic changes in lungs of mice flown on the
STS-135 mission in space. In Vivo. July 8, 2015;29:423-433.
Ishihara A, Nagatomo F, Terada M, Fujino H, Kondo H, Ishioka N. Effects of microgravity on the
mouse triceps brachii muscle. Muscle & Nerve. July 2015;52:63-68. doi: 10.1002/mus.24491.
Hwang S, Crucian BE, Sams CF, Actor JK. Post-spaceflight (STS-135) mouse splenocytes
demonstrate altered activation properties and surface molecule expression. PLOS ONE. May 13,
2015;10:e0124380. doi: 10.1371/journal.pone.0124380.
Ritchie LE, Taddeo SA, Weeks BR, et al. Space environmental factor impacts upon murine colon
microbiota and mucosal homeostasis. PLOS ONE. June 17, 2015;10:e0125792. doi:
10.1371/journal.pone.0125792.
Taylor CR, Hanna M, Behnke BJ, et al. Spaceflight-induced alterations in cerebral artery
vasoconstrictor, mechanical, and structural properties: Implications for elevated cerebral