1998 Fiscal Year Final Research Report Summary
Evaluation of a-adrenoceptor-mediated vasoconstriction to the subendocardial flow-coronary slosh phenomenon and intramyocardial arteriolar diameter change-
| Project/Area Number |
09670770
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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 |
Circulatory organs internal medicine
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| Research Institution | Kawasaki Medical School |
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Principal Investigator |
YADA Toyotaka Kawasaki Medical School, Medical Engineering, Assistant Professor, 医学部, 講師 (00210279)
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| Co-Investigator(Kenkyū-buntansha) |
MORITA Ichiro Kawasaki Medical School, Medical Engineering, Assistant Professor, 医学部, 講師 (30200413)
TABUCHI Atsushi Kawasaki Medical School, Medical Engineering, Assistant Professor, 医学部, 講師 (60236726)
NAKAMOTO Hiroshi Kawasaki Medical School, Medical Engineering, Research Associate, 医学部, 助手 (10299183)
OGASAWARA Yasuo Kawasaki Medical School, Medical Engineering, Associate Professor, 医学部, 助教授 (10152365)
KAJIYA Fumihiko Kawasaki Medical School, Medical Engineering, Professor, 医学部, 教授 (70029114)
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| Project Period (FY) |
1997 – 1998
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| Keywords | coronary vasoconstriction / alpha-adrenoreceptors / slosh phenomenon / Doppler velocimeter / phasic coronary flow / 冠血管トーヌス / 高速度CCD生体顕微鏡 |
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| Research Abstract |
There is alpha paradoxical a-adreno-ceptor-mediated coronary vasoconstriction whenever there is adrenergic activation of the heart, as during cardiovascular eflexes or exercise. The aim of the this study was to test the hypothesis that alpha-adrenoceptor-mediated vasoconstriction lessens the to-and-fro oscillation of blood flow that occurs in the coronary arterial tree during systole and diastole. Septal coronary artery blood velocity was measured in anesthetized open-chest dogs with a 20-MHz pulsed Doppler velocimeter. The blood flow velocity in the microvessels was visualized by the high-speed system using an optically shinning microspheres. Unlike epicardial arterial flow patterns, the velocity waveform was characterized by exclusively diastolic flow and by two peaked systolic reverse flow (early and mid-to-late systole, slosh phenomenon). Systolic retrograde velocity and diastolic forward velocity were compared during norepinephrine infusion before and after alpha-adrenoceptor bloc
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kade with phenoxybenzamine. Systo lic aortic pressure was held constant by aortic banding ; heart rate was controlled by pacing at 80, 140, and 200 beats/min ; and maximum left ventricular dP/dt was unchanged by alpha-blockade. At each pacing rate, systolic retro-grade velocity was significantly greater after alpha-blockade, indicating that alpha-vasoconstriction reduced systolic retrograde flow by changing coronary vascular impedance. Transmural blood flow was measured with microspheres in a second group of dogs during the same experimental conditions, and flow to the inner layer of the left ventricle was diminished by a-adrenoceptor blockade at a heart rate of 250 beats/min, demonstrating a beneficial effect of alpha-vasoconstriction. In conclusion, adrenergic alpha-adrenoceptor-mediated coronary vasoconstriction reduces systolic retrograde coronary flow during norepinephrine infusion. This lessens to-and-fro flow oscillation in the coronary circulation and probably is the mechanism whereby alpha-vasoconstriction helps maintain blood flow to the inner layer of the left ventricle during exercise. Less
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