title: Cardiovascular responses to simulated microgravity in Sprague-Dawley rats.
abstract: Microgravity is known to induce orthostatic intolerance and baroreflex impairment in astronauts. Cardiovascular responses observed in 30 degrees head-down tilt rat models, whether 24 hr whole body suspension (WBS) or 7 day tail-suspension (TS), mimic observations made during exposure to microgravity. We evaluated the cardiovascular effects of simulated microgravity and the subsequent post-suspension in rats using the above models. Mean arterial pressure (MAP) of both WBS and TS rats did not change during suspension. In both models, MAP decreased post-suspension and this response lasted for 6 hrs. Salt-loaded animals did not show a post-suspension reduction in MAP. Plasma ionized calcium was decreased at 2 hr of WBS, with no change in sodium, potassium, magnesium, glucose, or hematocrit. Body weight changes were similar for all animals whether under suspension or control conditions. Both rat models demonstrate post-suspension hypotension and these results support the notion that salt-loading may have some beneficial effects in ameliorating this hypotension.
authors.affiliation: Department of Pharmacology/Toxicology, Morehouse School of Medicine, Atlanta, GA 30310-1495, USA.
authors.forename: R R
authors.initials: RR
authors.lastname: Socci
authors.forename: M
authors.initials: M
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Thierry-Palmer
authors.forename: N
authors.initials: N
authors.lastname: Emmett
authors.forename: M A
authors.initials: MA
authors.lastname: Bayorh
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D002118:Calcium / Q000097:blood; D002395:Catecholamines / Q000097:blood; D004195:Disease Models, Animal; D006339:Heart Rate / Q000502:physiology*; D019417:Hindlimb Suspension / Q000502:physiology; D007024:Hypotension, Orthostatic / Q000097:blood / Q000209:etiology / Q000503:physiopathology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000502:physiology; D018474:Weightlessness Simulation
chemical_list: D002395:Catecholamines; D002118:Calcium