| Co-Investigator(Kenkyū-buntansha) |
MIYAMOTO Kazuyuki KAGAWA MEDICAL UNIVERSITY UNIVERSITY HOSPITAL, RESEARCH ASSOCIATE, 医学部・附属病院, 助手 (40325345)
OE Masahiro KAGAWA MEDICAL UNIVERSITY UNIVERSITY HOSPITAL, ASSISTANT PROFESSOR, 医学部・附属病院, 講師 (00279340)
鶴原 由一 香川医科大学, 医学部・附属病院, 助手 (50244025)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2000: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1999: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1998: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
During 1998-1999, renal sympathetic nerve activity (RNA) responses to acute cardiac tamponade (CT) were studied in conscious rabbits with all reflexes intact (INT) or after sinoaortic baroreceptor denervation (BRD) or cardiac nerve denervation (CND). In INT rabbits, the RNA increased to over 200% during the mean arterial pressure (MAP) mentained when the CT was started, whereas the RNA decreased to below half and at the same time the MAP decreased sharply by subsequent injection of saline. After that, an administration of naloxone resulted in increases in both MAP and RNA.If 7-nitroindazole was admitted before the biginning of CT, the decline in RNA caused by decompensated CT was markedly prevented and brain nitric oxide synthase activity in the cerebral cortex and medulla oblongata was inhibited by 48% and 44%. In BRD rabbits, RNA did not alter throughout CT, but increased on injection of naloxone. In CND rabbits, RNA increased during compensated CT but did not decrease during decompe
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nsated CT.These results indicate that RNA responses to CT are biphasic, with an increase during conpensated CT and a decrease during decompensated CT.Sinoaortic baroreceptors are involved in mediating the increase in RNA, whereas cardiac receptors may be involved in mediating the decrease in RNA The abrupt decrease in RNA during decompensated CT may be mediated by NO or endogenous opioid in the central nervous system.
In 2000, it was studied that the effects of cardiogenic or hemorrhagic shock on RNA and baroreflex. CT increased RNA initially, followed by decline below baseline. Vagotomy abolished the baroreflex attenuation. However, hemorrhagic shock increased RNA initially, followed by recovery toward baseline. Cervical vagotomy maintained RNA at higher level than those of INT rabbits on both shock. The baroreflex sensitivity was significantly attenuated soon after releasing CT.In contrast to CT, the baroreflex sinsitivity was not attenuated after hemorrhage recovering. These results indicated that sympathetic nerve activity may be attenuated more heavily in CT than hemorrhage, and cardiogenic shock attenuated the baroreflex via vagal afferents. Less
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