1991 Fiscal Year Final Research Report Summary
Effects if weightlessness simulated by a 24-hour recumbency on autonomic nervous system in man
| Project/Area Number |
02454256
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Circulatory organs internal medicine
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| Research Institution | Osaka University |
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Principal Investigator |
TAKEDA Hiroshi Osaka University Hospital, Associate Professor, 医学部附属病院, 助教授 (20127252)
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| Co-Investigator(Kenkyū-buntansha) |
OZAKI Hitoshi Osaka University Hospital Clinical Fellow, 医学部附属病院, 医員
SATO Hideyuki Osaka university Medical School Assistant, 医学部, 助手 (70167435)
KITABATAKE Akira Osaka University Medical School Associate Professor, 医学部, 助教授 (00124769)
INOUE Michitoshi Osaka University Hospital Professor, 医学部附属病院, 教授 (30028401)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Weightlessness / 24-hour recumbency / Sympathetic nerve / Para Sympathetic nerve / Baroreflex / Orthostatic stress |
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| Research Abstract |
Orthostatic intolerance and increases in heart rate and vasoconstrictive response to orthostatic stress observed after a space flight has been explained by circulating blood volume loss. However, it is also possible that changes in arterial baroreflex sensitivity or target organ sensitivities to sympathetic stimulation account for these abnormalities. To investigate the mechanisms for the abnormal responses to orthostatic stress after a space flight, we studied effects of a 24hour recumbency on the arterial baroreflex sensitivity and catecholamine sensitivities of the heart and vessels in 5 healthy subjects. After a 24-hour recumbency heart rate and forean-n vasoconstrictor responses to lower body negative pressure were increased compared to those before the recumbency. The body weight was decreased by recumbency, suggesting loss of circulating blood volume. The arterial baroreflex sensitivity decreased whereas heart rate and vasoconstrictor responses to exogenous catecholamines were increased. These results suggest that although a d in blood volume primarily accounts for orthostatic intolerance after a space flight, increased hemodynamic responses to orthostatic stress are resulted from an increase in catecholamine sensitivity of target organs in addition to blood volume loss. The decrease in arterial baroreflex sensitivity may counteract the hemodynamic hyperactivities.
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