title: Arterial pressure oscillation and muscle sympathetic nerve activity after 20 days of head-down bed rest.
abstract: Both spectral power within the low-frequency component, i.e., 0.04 to 0.15 Hz, of systolic pressure and muscle sympathetic nerve activity are increased during head-up tilt. The nerve activity during tilt is altered after space flight and exposure to simulated microgravity. In the present study, correlations of the low-frequency component and the nerve activity were analyzed before and after 20 days of -6° of head-down bed rest. Measurements were performed at -6° head-down bed rest, 0° (flat), and 30° and 60° head-up tilt (HUT). Mean arterial pressure during HUT was not different between pre- and post-bed rest, but muscle sympathetic nerve activity in post-bed rest significantly increased at tilt angles of -6°, 0°, 30°, and 60° compared with those during pre-bed rest. The low-frequency component of systolic pressure also significantly increased during post-bed rest compared with pre-bed rest at tilts of 0°, 30°, and 60°. The nerve activity and the frequency component were linearly correlated for individual (r(2) = 0.51-0.88) and averaged (r(2) = 0.60) values when the values included both pre- and post-bed rest. Thus, the low-frequency component of systolic pressure could be an index of the muscle sympathetic nerve activity during tilt during pre- and post-bed rest.
authors.affiliation: Department of Radiotechnology, Gifu University of Medical Science, Gifu, 501-3892, Japan; Department of Physiology, Graduate School of Medicine, Gifu University, Gifu, 501-1194, Japan. Electronic address: ktanaka@u-gifu-ms.ac.jp.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tanaka
authors.forename: Naoki
authors.initials: N
authors.lastname: Nishimura
authors.forename: Maki
authors.initials: M
authors.lastname: Sato
authors.forename: Dominika
authors.initials: D
authors.lastname: Kanikowska
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Yoko
authors.initials: Y
authors.lastname: Inukai
authors.forename: Chikara
authors.initials: C
authors.lastname: Abe
authors.forename: Chihiro
authors.initials: C
authors.lastname: Iwata
authors.forename: Hironobu
authors.initials: H
authors.lastname: Morita
authors.forename: Satoshi
authors.initials: S
authors.lastname: Iwase
authors.forename: Junichi
authors.initials: J
authors.lastname: Sugenoya
mesh_terms: D000328:Adult; D062186:Arterial Pressure / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology; D001510:Bed Rest / Q000379:methods*; D018475:Head-Down Tilt / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D016683:Supine Position / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors; D018474:Weightlessness Simulation / Q000379:methods* / Q000639:trends; D055815:Young Adult
keywords: Low-frequency component; Microgravity; Power spectral analysis