Effect of short-term microgravity and long-term hindlimb unloading on rat cardiac mass and function

Ray, Chester A.; Vasques, Marilyn; Miller, Todd A.; Wilkerson, M. Keith; Delp, Michael D.

doi:10.1152/jappl.2001.91.3.1207

Cited by 35 publications

(22 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has been reported that sedentary animals show enhanced sympathoexcitation and altered sympathetic control of blood pressure [42], [43]. Our unloaded rat data are in accordance with what is cited in the literature, even considering differences in the methods of cardiovascular parameter measurements [17], [44], [45]. Unloading caused very similar changes in blood pressure when compared to the group of attached animals, where an increase of diastolic pressure and dramatic rise of SBP was accompanied by a significant perturbation of the day-night cycle.…”

Section: Discussionsupporting

confidence: 92%

Contribution of Social Isolation, Restraint, and Hindlimb Unloading to Changes in Hemodynamic Parameters and Motion Activity in Rats

et al. 2012

View full text Add to dashboard Cite

The most accepted animal model for simulation of the physiological and morphological consequences of microgravity on the cardiovascular system is one of head-down hindlimb unloading. Experimental conditions surrounding this model include not only head-down tilting of rats, but also social and restraint stresses that have their own influences on cardiovascular system function. Here, we studied levels of spontaneous locomotor activity, blood pressure, and heart rate during 14 days under the following experimental conditions: cage control, social isolation in standard rat housing, social isolation in special cages for hindlimb unloading, horizontal attachment (restraint), and head-down hindlimb unloading. General activity and hemodynamic parameters were continuously monitored in conscious rats by telemetry. Heart rate and blood pressure were both evaluated during treadmill running to reveal cardiovascular deconditioning development as a result of unloading. The main findings of our work are that: social isolation and restraint induced persistent physical inactivity, while unloading in rats resulted in initial inactivity followed by normalization and increased locomotion after one week. Moreover, 14 days of hindlimb unloading showed significant elevation of blood pressure and slight elevation of heart rate. Hemodynamic changes in isolated and restrained rats largely reproduced the trends observed during unloading. Finally, we detected no augmentation of tachycardia during moderate exercise in rats after 14 days of unloading. Thus, we concluded that both social isolation and restraint, as an integral part of the model conditions, contribute essentially to cardiovascular reactions during head-down hindlimb unloading, compared to the little changes in the hydrostatic gradient.

show abstract

Section: Discussionsupporting

confidence: 92%

Contribution of Social Isolation, Restraint, and Hindlimb Unloading to Changes in Hemodynamic Parameters and Motion Activity in Rats

et al. 2012

View full text Add to dashboard Cite

show abstract

“…More recent use of magnetic resonance imaging revealed an average 14% reduction in the left ventricular mass of four astronauts following their 10-day mission, supporting the hypothesis that the smaller cardiac size observed after space flight reflected atrophy of myocardial muscle [40]. Contrary to the notion of myocardial atrophy, recent evidence generated from ground-based and flight experiments on animals suggests that smaller myocardial mass may reflect simply the impact of negative caloric balance and body mass routinely observed in astronauts during space flight [41]. Since the loss of body fluids represents a significant amount of body mass reduction in astronauts, it is possible that the apparent reduction in cardiac size represents a loss in tissue water rather than muscle atrophy.…”

Section: Cardiac Structural and Functional Adaptationsmentioning

confidence: 61%

Cardiovascular Consequences of Weightlessness Promote Advances in Clinical and Trauma Care

Cooke¹,

Convertino²

2005

CPB

View full text Add to dashboard Cite

Cardiovascular adaptations driven by exposure to weightlessness cause some astronauts to experience orthostatic intolerance upon return to Earth. Maladaptations of spaceflight that lead to hemodynamic instability are temporary, and therefore astronauts provide for researchers a powerful model to study cardiovascular dysfunction in terrestrial patients. Orthostatic intolerance in astronauts is linked to changes in the autonomic control of cardiovascular function, and so patients that suffer neurocardiogenic syncope may benefit from a greater understanding of the effects of spaceflight on the autonomic nervous system. In addition, appropriate autonomic compensation is fundamental to the maintenance of stable arterial pressures and brain blood flow in patients suffering traumatic bleeding injuries. The application of lower body negative pressure (LBNP), an experimental procedure used widely in aerospace physiology, induces autonomic and hemodynamic responses that are similar to actual hemorrhage and therefore may emerge as a useful experimental tool to simulate hemorrhage in humans. Observations that standing astronauts and severely injured patients are challenged to maintain venous return has contributed to the development of an inspiratory impedance threshold device that serves as a controlled "Mueller maneuver" and has the potential to reduce orthostatic intolerance in returning astronauts and slow the progression to hemorrhagic shock in bleeding patients. In this review, we focus on describing new concepts that have arisen from studies of astronauts, patients, and victims of trauma, and highlight the necessity of developing the capability of monitoring medical information continuously and remotely. Remote medical monitoring will be essential for long-duration space missions and has the potential to save lives on the battlefield and in the civilian sector.

show abstract

“…The 'hindlimb-unloaded rat' is a model for autonomic deconditioning [28,55]. The rat's hind limbs are bound and its body is suspended using a trolley, so the rat can move about using its forepaws.…”

Section: Orthostatic Syncope S Manmentioning

confidence: 99%

“…This model mimics space flight, which abolishes normal gravitational stress. It causes many alterations similar to those in astronauts [28,55]. Whether or not they (the rats) fainted was not specified.…”

Section: Orthostatic Syncope S Manmentioning

confidence: 99%

Fainting in animals

Dijk

2003

Clin Auton Res

View full text Add to dashboard Cite

Fainting (syncope) is unconsciousness due to insufficient cerebral circulation in the context of a temporary failure of the systemic circulation. This paper firstly aims to discuss fainting in animals, and secondly to discuss animal physiology to broaden the understanding of human fainting. Of the three major syncope types (cardiac, orthostatic and reflex syncope), only cardiac syncope occurs in animals as in man, through arrhythmia or output failure. Man's orthostatic fainting tendency has been blamed on his upright posture. A comparison with animals shows that giraffes, tree climbing snakes, and animals that quickly raise and lower their heads face more serious gravitational circulatory challenges than man, but do not appear to faint. Merely carrying the brain above the heart does not explain a fainting tendency, as the human heart-to-brain height is smaller than that of many mammals with similar blood pressure. Two evolutionary novelties may be to blame: the proportion of cardiac output going upwards to the brain is much larger than in apes, and man's large legs suggest that the volume lost to venous pooling is also larger. Emotional factors play a role in many reflex syncope events. Tonic immobility ('feigning death','playing possum') is not a good model, as it concerns immobility as a survival strategy of an attentive brain, rather than unconsciousness due to circulatory breakdown. Whether orienting and defense responses form a valid model remains to be proven. Emotional fainting may be uniquely human; how mental processes can shut down the circulation and thereby the brain needs serious study, as it may hold the key to syncope prevention.

show abstract

Effect of short-term microgravity and long-term hindlimb unloading on rat cardiac mass and function

Cited by 35 publications

References 30 publications

Contribution of Social Isolation, Restraint, and Hindlimb Unloading to Changes in Hemodynamic Parameters and Motion Activity in Rats

Contribution of Social Isolation, Restraint, and Hindlimb Unloading to Changes in Hemodynamic Parameters and Motion Activity in Rats

Cardiovascular Consequences of Weightlessness Promote Advances in Clinical and Trauma Care

Fainting in animals

Contact Info

Product

Resources

About