Adrenergic vascular control.
The gravity-dependency and age-dependency of noradrenergic vasoconstrictor outflow to skeletal muscle (muscle sympathetic nerve activity; MSNA) in humans was analyzed by applying microneurography technique. The basal level of MSNA in the horizontally supine position increased with aging without significant changes in arterial baroreflex sensitivity. MSNA responded to +Gz load by head-up tilt and to simulated microgravity by thermoneutral head-out immersion with increasing and decreasing the activity, respectively. These gravity related responses of MSNA were age-dependent, being reduced by aging. Simultaneously monitored hemodynamic responses to +Gz load and to simulated microgravity were also age-dependent, being reduced by aging. The gravity-dependent and also age-dependent changes in the noradrenergic vasoconstrictor outflow to muscle seem to be related to the mechanisms controlling the gravity-dependent fluid shift in the human body.
Department of Autonomic and Behavioral Neurosciences, Nagoya University, Japan.
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D000293:Adolescent; D000320:Adrenergic Fibers / Q000502:physiology*; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D006112:Gravitation; D006801:Humans; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000294:innervation; D012039:Regional Blood Flow; D013564:Sympathetic Nervous System / Q000502:physiology*; D018474:Weightlessness Simulation