Subnormal norepinephrine release relates to presyncope in astronauts after spaceflight

Fritsch-Yelle, Janice M.; Whitson, Peggy A.; Bondar, Roberta L.; Brown, Troy E.

doi:10.1152/jappl.1996.81.5.2134

Cited by 207 publications

(217 citation statements)

References 25 publications

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“…shown that astronauts who are orthostatic intolerant exhibit a significantly lower norepinephrine response to standing than their tolerance counterparts (Fritsch-Yelle et al 1996).…”

Section: Cardiovascular System and Deconditioningmentioning

confidence: 99%

A critical benefit analysis of artificial gravity as a microgravity countermeasure

2010

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Human physiological systems, especially the cardiovascular and musculo-skeletal systems, are well-known to decondition during spaceflight. Several countermeasures that are in use today have been rigorously developed over the decades to combat this deconditioning. However, these countermeasures are system specific and have proven to be only partially effective. Artificial gravity has been persistently discussed as a countermeasure that potentially has salutary effects on all physiological systems, though few ground-based studies have been performed in comparison to other countermeasures. The current analysis attempts to elucidate the effectiveness of artificial gravity by directly comparing results of previously published and unpublished deconditioning studies with those of more traditional, ground-based countermeasures (i.e. resistive exercise, aerobic exercise, lower body negative pressure, or some variation of these). Animal studies were also evaluated to supplement the knowledge base and to fill gaps in the human countermeasure literature. Designs of published studies, such as study duration, deconditioning paradigm, subject selection criteria, measurements taken, etc., were confounding variables; however, studies that had some measure of consistency between these variables were compared, although notable differences were cited in the analysis and discussion. Results indicate that for prolonged spaceflight an artificial gravity-based countermeasure may provide benefits equivalent to traditional countermeasures for the cardiovascular system. Too few comparable, human studies have been performed to draw any conclusions for the musculoskeletal system, although animal studies show some positive results. Gaps in the current knowledge of artificial gravity are identified and guidance for future deconditioning studies is offered. Based on the results of this study, a comprehensive artificial gravity protocol is proposed and future research topics using this countermeasure are

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“…shown that astronauts who are orthostatic intolerant exhibit a significantly lower norepinephrine response to standing than their tolerance counterparts (Fritsch-Yelle et al 1996).…”

Section: Cardiovascular System and Deconditioningmentioning

confidence: 99%

A critical benefit analysis of artificial gravity as a microgravity countermeasure

2010

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“…8 On the other hand, women (all non-finishing) were shown to have the ability to increase their TPR from supine to standing by margins even larger than most male finishers, but had lower pretest TPR and blood pressure, as well as a higher arterial pressure threshold at which presyncope occurred. 18 This comparison suggests that while an increase in TPR may be necessary to maintain arterial pressure and prevent presyncope, it may be insufficient if pretest arterial pressure is too near to its presyncopal threshold.…”

Section: Introductionmentioning

confidence: 97%

Simulated Stand Tests and Centrifuge Training to Prevent Orthostatic Intolerance on Earth, Moon, and Mars

Coats

Sharp

2010

Ann Biomed Eng

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Abstract-One proposed method to overcome postflight orthostatic intolerance is for astronauts to undergo inflight centrifugation. Cardiovascular responses were compared between centrifuge and gravitational conditions using a seven-compartment cardiovascular model. Vascular resistance, heart rate, and stroke volume values were adopted from literature, while compartmental volumes and compliances were derived from impedance plethysmography of subjects (n = 8) riding on a centrifuge. Three different models were developed to represent the typical male subject who completed a 10-min postflight stand test (''male finisher''), ''non-finishing male'' and ''female'' (all non-finishers). A sensitivity analysis found that both cardiac output and arterial pressure were most sensitive to total blood volume. Simulated stand tests showed that female astronauts were more susceptible to orthostatic intolerance due to lower initial blood pressure and higher pressure threshold for presyncope. Rates of blood volume loss by capillary filtration were found to be equivalent in female and male non-finishers, but four times smaller in male finishers. For equivalent times to presyncope during centrifugation as those during constant gravity, lower G forces at the level of the heart were required. Centrifuge G levels to match other cardiovascular parameters varied depending on the parameter, centrifuge arm length, and the gravity level being matched.

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“…However, on return to earth, from one-quarter to twothirds of them have reduced orthostatic tolerance for a few weeks. The underlying molecular mechanisms remain unknown and are probably multifactorial, although alterations in the autonomic nervous system and/or neuromuscular function after spaceflight probably contribute to this problem (18,19).…”

Section: +mentioning

confidence: 99%

“…Many astronauts suffer to varying degrees from symptoms suggestive of autonomic dysfunction such as nausea, vomiting, and dizziness during the early days of space flight (17), as well as showing severe orthostatic intolerance for several days after spaceflight (18,19). The underlying molecular mechanism and appropriate treatment for the autonomic dysfunction in space and on earth after space flight remain unknown.…”

Section: Introductionmentioning

confidence: 99%

Pharmacological Stimulation of Type 5 Adenylyl Cyclase Stabilizes Heart Rate Under Both Microgravity and Hypergravity Induced by Parabolic Flight

et al. 2012

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Abstract. We previously demonstrated that type 5 adenylyl cyclase (AC5) functions in autonomic regulation in the heart. Based on that work, we hypothesized that pharmacological modulation of AC5 activity could regulate the autonomic control of the heart rate under micro-and hypergravity. To test this hypothesis, we selected the approach of activating AC5 activity in mice with a selective AC5 activator (NKH477) or inhibitor (vidarabine) and examining heart rate variability during parabolic flight. The standard deviation of normal R-R intervals, a marker of total autonomic variability, was significantly greater under micro-and hypergravity in the vidarabine group, while there were no significant changes in the NKH477 group, suggesting that autonomic regulation was unstable in the vidarabine group. The ratio of low frequency and high frequency (HF) in heart rate variability analysis, a marker of sympathetic activity, became significantly decreased under micro-and hypergravity in the NKH477 group, while there was no such decrease in the vidarabine group. Normalized HF, a marker of parasympathetic activity, became significantly greater under micro-and hypergravity in the NKH477 group. In contrast, there was no such increase in the vidarabine group. This study is the first to indicate that pharmacological modulation of AC5 activity under micro-and hypergravity could be useful to regulate the autonomic control of the heart rate.

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Subnormal norepinephrine release relates to presyncope in astronauts after spaceflight

Cited by 207 publications

References 25 publications

A critical benefit analysis of artificial gravity as a microgravity countermeasure

A critical benefit analysis of artificial gravity as a microgravity countermeasure

Simulated Stand Tests and Centrifuge Training to Prevent Orthostatic Intolerance on Earth, Moon, and Mars

Pharmacological Stimulation of Type 5 Adenylyl Cyclase Stabilizes Heart Rate Under Both Microgravity and Hypergravity Induced by Parabolic Flight

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