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PubMed · 12124182

Salt-loading and simulated microgravity on baroreflex responsiveness in rats.

M A Bayorh·R R Socci·M Wang·N Emmett·M Thierry-Palmer
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Abstract

Cardiovascular adaptations observed during exposure to microgravity results in impairment of baroreflex activity partially as a result of fluid and electrolyte shifts. The head-down tilt rat model mimics some of the physiological observations that have been made in astronauts. We examined the effects of salt-loading on baroreflex activity after 7 day simulated microgravity (30 degrees tail-suspension) and the subsequent 6 hr post-suspension in Sprague-Dawley (SD) rats, using low salt (0.3% NaCl) and high salt (8% NaCl) diets. In suspended animals on a low salt diet, the baroreflex response curve was shifted to the left, while the heart rate (HR) range and MAP50 values were reduced compared to their parallel tethered, non-suspended controls. For non-suspended animals, salt-loading shifted the curve to the right with a reduced HR range. In salt-loaded, suspended animals, the curve and its parameters resemble those of non-suspended animals on a low salt diet. In summary, these data have demonstrated that a short-term (seven days) simulated weightlessness may elicit cardiovascular deconditioning in rats after release from the simulation manifested as an altered responsiveness in baroreceptor-heart rate reflex and a lowered blood pressure while the rats are tethered and horizontal. Our results also suggest the counteracting effect of salt loading on cardiovascular deconditioning.

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AnimalsBaroreflexBlood PressureCardiovascular DeconditioningDiet, Sodium-RestrictedDose-Response Relationship, DrugHead-Down TiltHindlimb SuspensionMaleModels, AnimalRatsRats, Sprague-DawleySodium, DietaryWeightlessness CountermeasuresWeightlessness SimulationNASA Discipline CardiopulmonaryNon-NASA CenterComparative StudyJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

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M A Bayorh, R R Socci, M Wang, N Emmett, M Thierry-Palmer. 2000. Salt-loading and simulated microgravity on baroreflex responsiveness in rats.. https://pubmed.ncbi.nlm.nih.gov/12124182/

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