Acute Effects of 6ﾟ Head Down Bed Rest on Carotid Baroreflex and Cerebrovascular Hemodynamic in Human
| Project/Area Number |
09670078
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental physiology (including Physical medicine and Nutritional physiology)
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| Research Institution | St.Marianna University School of Medicine |
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Principal Investigator |
KAMEGAI Manabu St.Marianna University School of Medicine, The Medical Department, Assistant Professor., 医学部, 助教授 (60169638)
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| Co-Investigator(Kenkyū-buntansha) |
堀田 宗文 聖マリアンナ医科大学, 医学部, 助手 (40308507)
SASAKI Toshio St.Marianna University School of Medicine, The Medical Department, Research Asso, 医学部, 助手 (30277983)
渡辺 みどり 聖マリアンナ医科大学, 医学部, 助手 (80257360)
KAMO Tsutomu St.Marianna University School of Medicine, The Medical Department, Lectures., 医学部, 講師 (20224701)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
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| Keywords | microgravity / posture change / cardiovascular hemodynamic / cerebral circulation / baroreflex / autonomic nervous system / neck suction / bed rest / ヘッドダウンベッドレスト / 圧受容器反射 / 体循環動態 / 脳循環動態 / ネックサクション / 模擬無重力 / 適応反応 |
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| Research Abstract |
The authors studied acute effects of carotid baroreflex function and cerebral circulation during 4 hours 6 Head Down Bed Rest(6HDBR) and 1 hour horizontal bed rest(OBR) after the following basic studies. (1)To examine the neck suction (NS) method of evaluating carotid baroreceptor function, we evaluated carotid baroreceptor reflex sensitivity (BRS) by measuring changes in heart rate and blood pressure induced by the NS method, and compared BRS evaluated by NS method with BRS evaluated by the conventional phenylephrine method. In additon, to reveal the characteristica of baroreflex responce to change in carotid sinus pressure(CSP), we evaluated BRS using the NS method and varying the rate of change in NS pressure(dp/dt). The NS method was shown to be as effective in evaluating BRS as the conventional phenylephrine method. It was shown that an increase in pulse pressure was a factor in stimulating the carotid baroreceptor when the NS method was used. The characteristics of the baroreflex
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response to change in dp/dt of CSP could be observed in the NS method in order that a positive correlation was observed between BRS and dp/dt. (2)To investigated the baroreflex-mediated autonomic mechanisms involved in the pathogenesis of syncope, hemodynamic changes were examined during orthostatic stress loading by saddle support head-up tilt. This study indicated that baroreflex-mediated autonomic mechanisms other than enhancement of vasomotor aipha-adrenergic activity may make a greater contribution to the maintenance of blood pressure during orthostatic stress in syncope. (3)To investigated the changes of baroreflex-mediated autonomic function against posture change, the autonomic activity evaluated by spectral analysis of heart rate and blood pressure variability was examined during orthostatic stress loading by lower body negative pressure. In this study, it was inferred that cardiac vagal efferent activity is inhibited at early stage via inhibition of the baroreflex during. Reflex control results in an exacerbration of vasomotor sympathetic activity which reaches a peak after 3 minutes of orthostatic stress.
The changes of carotid baroreflex function and cerebrovascular hemodynamic during 6HDBR and OBR evaluated by NS method were following.
(1)The decreasing of vasopressin and norepinepfrine were observed during both 6HDBR and OBR.These changes were effected by term of bed rest. However, BRS was increased during 6HDBR, and was deceased during OBR after 6HDBR with no changes in base line blood pressure and heart rate. Therefore, baroreflex responces to posture chanege in differnce of 6 degrees in acute phase of bed rest. (2)The baroreflex responce to change in dp/dt of carotic sinus pressure unchanged during 6HDBR and BR with the decreasing of sympathetic activity and increasing of parasympathetic activity. (3)The cerebrovascular contol stimulated by carotid baroreflex using NS method unchanged during 6HDBR and OBR.In previous study, we reported that the cerebrovascular responce in stimulation of carotid baroreceptor depends on changing of mean blood pressure after prolonged 6HDBR.In conclusion, the neural controls of cardiovascular and cerebrovascular hemodynamic are different between 6HDBRand OBR in acute phase. Less
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Report
(3 results)
Research Products
(6 results)
