RESPONSES OF CEREBRAL ARTERIES TO THE CHANGE OF CEREBRAL PERFUSION PRESSURE Shuhei Yamaguchi 1,2 , Shotai Kobayashi 1 , Kazuya Yamashiata 1 , Akihiro Murata 1 , Mitsuhiro Kitani 1 1Third Division of Internal Medicine, Shimane Medical University 2Present Address: Department of Neurology, VA Medical Center pp.807-811
Published Date 1989/8/1
DOI https://doi.org/10.11477/mf.1406206371
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The responsiveness of cerebral pial a rterie;and arterioles to changes in systemic arterial blood pressure (SAP) was investigated. Using 9 cats anesthetized with chloralose and urethane, direct, simultaneous measurements of pial arterial pressure (PAP) and cerebral blood flow (CBF) were made during changes in SAP. SAP was varied between 25 and 140 mmHg by the hemor-rhage and blood infusion methods. After a partial craniotomy, PAP was measured with a micro-pipette connected to a servo-controlled micropres-sure recording system. Punctured pial arteries were grouped into three types according to their diameters, 1A (291 ± 33 pm), 2A (16 ± 26 pm), and 3A (70±10 Atm). CBF on the exposed cortex was measured with hydrogen clearance method.

The PAPs measured were a linear function of SAP; PAP (1 A)= 0. 73 x SAP ? 6. 6 (r = 0. 96) , PAP (2A) = O. 62 x SAP ? 6. 6 (r = 0. 90) , PAP (3A) = O. 61 x SAP ? 6. 4 (r = 0. 93). This result indicates that PAPs are entirely dependent on SAP and that SAP induced changes in PAPs are less in the smaller pial arteries. Regional CBF remained constant (55±4 ml/100 g/min) between 60 and 140 mmHg of SAP. A significant decrease in CBF was observed below 60 mmHg of SAP.

Cerebrovascular resistances were calculated segmentally using the following formulas ; large vessel resistances (LVR)= (SAP ? PAP (1A))/CBF, middle vessel resistance= (PAP (1 A) ? PAP (3 A))/ CBF, and small vessel resistance= PAP (3 A)/CBF. The changes in LVR, MVR, and SVR were almost identical between 70 and 140 mmHg of SAP. Below 70 mmHg of SAP, SVR showed the greatest decrease in resistance. When SAP was further decreased below 50 mmHg, LVR showed a rapid increase. The ratio of resistance in each sized artery to the total cerebrovascular resistance was calculated as a function of SAP. In the control state, LVR, MVR and SVR was 35.6± 2.8%, 9. 4 ± 2. 9% and 55. 0 ± 2. 8%, respectively. Below 70 mmHg of SAP the ratio of SVR to the total resistance fell rapidly. At 35 mmHg of SAP, SVR occupied only 26. 0± 2. 5% of the total resistance.

The results indicate that small pial arteries play a major role in the response of cerebral vasculature to decreased perfusion pressure when SAP is within a normal range of autoregulation. Below the range of autoregulation, large pial arteries have a large effect on the cerebrovascular resistance. The current study suggests that vas-cular size and systemic blood pressure are critical factors in evaluating the effects of vasoactive agents on cerebral circulation.

Copyright © 1989, Igaku-Shoin Ltd. All rights reserved.


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