title: Responses of neuromuscular systems under gravity or microgravity environment.
abstract: Hindlimb suspension of rats induces induces fiber atrophy and type shift of muscle fibers. In contrast, there is no change in the cell size or oxidative enzyme activity of spinal motoneurons innervating muscle fibers. Growth-related increases in the cell size of muscle fibers and their spinal motoneurons are inhibited by hindlimb suspension. Exposure to microgravity induces atrophy of fibers (especially slow-twitch fibers) and shift of fibers from slow- to fast-twitch type in skeletal muscles (especially slow, anti-gravity muscles). In addition, a decrease in the oxidative enzyme activity of spinal motoneurons innervating slow-twitch fibers and of sensory neurons in the dorsal root ganglion is observed following exposure to microgravity. It is concluded that neuromuscular activities are important for maintaining metabolism and function of neuromuscular systems at an early postnatal development and that gravity effects both efferent and afferent neural pathways.
authors.affiliation: Laboratory of Neurochemistry, Graduate School of Human and Environmental Studies, Kyoto University.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ishihara
authors.forename: Fuminori
authors.initials: F
authors.lastname: Kawano
authors.forename: Xiao Dong
authors.initials: XD
authors.lastname: Wang
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Ohira
mesh_terms: D000344:Afferent Pathways; D000818:Animals; D004525:Efferent Pathways; D004576:Electromyography; D006112:Gravitation; D019417:Hindlimb Suspension / Q000009:adverse effects*; D008159:Lumbar Vertebrae / Q000294:innervation; D009046:Motor Neurons / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D009133:Muscular Atrophy / Q000503:physiopathology; D051381:Rats; D013026:Space Flight; D013116:Spinal Cord / Q000166:cytology / Q000201:enzymology / Q000502:physiology; D014893:Weightlessness / Q000009:adverse effects*; D018474:Weightlessness Simulation / Q000009:adverse effects