title: Hindlimb unloading: rodent analog for microgravity.
abstract: The rodent hindlimb unloading (HU) model was developed in the 1980s to make it possible to study mechanisms, responses, and treatments for the adverse consequences of spaceflight. Decades before development of the HU model, weightlessness was predicted to yield deficits in the principal tissues responsible for structure and movement on Earth, primarily muscle and bone. Indeed, results from early spaceflight and HU experiments confirmed the expected sensitivity of the musculoskeletal system to gravity loading. Results from human and animal spaceflight and HU experiments show that nearly all organ systems and tissues studied display some measurable changes, albeit sometimes minor and of uncertain relevance to astronaut health. The focus of this review is to examine key HU results for various organ systems including those related to stress; the immune, cardiovascular, and nervous systems; vision changes; and wound healing. Analysis of the validity of the HU model is important given its potential value for both hypothesis testing and countermeasure development.
authors: Space Biosciences Division, NASA-Ames Research Center, Moffett Field, California ruth.k.globus@nasa.gov.
authors: Ruth K
authors: RK
authors: Globus
authors: Space Biosciences Division, NASA-Ames Research Center, Moffett Field, California.
authors: Emily
authors: E
authors: Morey-Holton
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000502:physiology; D006614:Hindlimb / Q000502:physiology*; D019417:Hindlimb Suspension / Q000502:physiology*; D006801:Humans; D009132:Muscles / Q000502:physiology; D012377:Rodentia / Q000502:physiology*; D013026:Space Flight / Q000379:methods; D014893:Weightlessness / Q000009:adverse effects*; D018474:Weightlessness Simulation / Q000379:methods
keywords: adaptation; gravity; hindlimb unloading; physiology; spaceflight