Document Detail

Differential blood flow responses to CO₂ in human internal and external carotid and vertebral arteries.
MedLine Citation:
PMID:  22526884     Owner:  NLM     Status:  MEDLINE    
Arterial CO2 serves as a mediator of cerebral blood flow(CBF), and its relative influence on the regulation of CBF is defined as cerebral CO2 reactivity. Our previous studies have demonstrated that there are differences in CBF responses to physiological stimuli (i.e. dynamic exercise and orthostatic stress) between arteries in humans. These findings suggest that dynamic CBF regulation and cerebral CO2 reactivity may be different in the anterior and posterior cerebral circulation. The aim of this study was to identify cerebral CO2 reactivity by measuring blood flow and examine potential differences in CO2 reactivity between the internal carotid artery (ICA), external carotid artery (ECA) and vertebral artery (VA). In 10 healthy young subjects, we evaluated the ICA, ECA, and VA blood flow responses by duplex ultrasonography (Vivid-e, GE Healthcare), and mean blood flow velocity in middle cerebral artery (MCA) and basilar artery (BA) by transcranial Doppler (Vivid-7, GE healthcare) during two levels of hypercapnia (3% and 6% CO2), normocapnia and hypocapnia to estimate CO2 reactivity. To characterize cerebrovascular reactivity to CO2,we used both exponential and linear regression analysis between CBF and estimated partial pressure of arterial CO2, calculated by end-tidal partial pressure of CO2. CO2 reactivity in VA was significantly lower than in ICA (coefficient of exponential regression 0.021 ± 0.008 vs. 0.030 ± 0.008; slope of linear regression 2.11 ± 0.84 vs. 3.18 ± 1.09% mmHg−1: VA vs. ICA, P <0.01). Lower CO2 reactivity in the posterior cerebral circulation was persistent in distal intracranial arteries (exponent 0.023 ± 0.006 vs. 0.037 ± 0.009; linear 2.29 ± 0.56 vs. 3.31 ± 0.87% mmHg−1: BA vs. MCA). In contrast, CO2 reactivity in ECA was markedly lower than in the intra-cerebral circulation (exponent 0.006 ± 0.007; linear 0.63 ± 0.64% mmHg−1, P <0.01). These findings indicate that vertebro-basilar circulation has lower CO2 reactivity than internal carotid circulation, and that CO2 reactivity of the external carotid circulation is markedly diminished compared to that of the cerebral circulation, which may explain different CBF responses to physiological stress.
Kohei Sato; Tomoko Sadamoto; Ai Hirasawa; Anna Oue; Andrew W Subudhi; Taiki Miyazawa; Shigehiko Ogoh
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-04-23
Journal Detail:
Title:  The Journal of physiology     Volume:  590     ISSN:  1469-7793     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-07-24     Completed Date:  2012-11-30     Revised Date:  2013-07-16    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  3277-90     Citation Subset:  IM    
Research Institute of Physical Fitness, Japan Women's College of Physical Education, Kita-Karasuyama, Setagaya-ku, Tokyo 157-8565, Japan.
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MeSH Terms
Blood Flow Velocity / physiology
Brain / blood supply*
Carbon Dioxide / blood*
Carotid Artery, External / ultrasonography*
Carotid Artery, Internal / ultrasonography*
Cerebrovascular Circulation / physiology
Hypercapnia / physiopathology
Hypocapnia / physiopathology
Regional Blood Flow / physiology
Ultrasonography, Doppler, Transcranial
Vertebral Artery / ultrasonography*
Reg. No./Substance:
124-38-9/Carbon Dioxide
Comment In:
J Physiol. 2012 Oct 15;590(Pt 20):4981-2   [PMID:  23082026 ]
J Physiol. 2012 Jul 15;590(Pt 14):3217   [PMID:  22826302 ]

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