The respiratory chemoreflex is known to be modified during orthostatic stress although the underlying mechanisms remain to be established. To determine the potential role of cerebral hypoperfusion, we examined the relationship between changes in MCA Vmean (middle cerebral artery mean blood velocity) and V̇E (pulmonary minute ventilation) from supine control to LBNP (lower body negative pressure; −45mmHg) at different CO2 levels (0, 3.5 and 5% CO2). The regression line of the linear relationship between V̇E and PETCO2 (end-tidal CO2) shifted leftwards during orthostatic stress without any change in sensitivity (1.36±0.27 l/min per mmHg at supine to 1.06±0.21 l/min per mmHg during LBNP; P=0.087). In contrast, the relationship between MCA Vmean and PETCO2 was not shifted by LBNP-induced changes in PETCO2. However, changes in V̇E from rest to LBNP were more related to changes in MCA Vmean than changes in PETCO2. These findings demonstrate for the first time that postural reductions in CBF (cerebral blood flow) modified the central respiratory chemoreflex by moving its operating point. An orthostatically induced decrease in CBF probably attenuated the ‘washout’ of CO2 from the brain causing hyperpnoea following activation of the central chemoreflex.
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Research Article|
March 13 2013
Cerebral hypoperfusion modifies the respiratory chemoreflex during orthostatic stress
Shigehiko Ogoh;
*Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
Correspondence: Dr Shigehiko Ogoh (email ogoh@toyo.jp).
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Hidehiro Nakahara;
Hidehiro Nakahara
†Morinomiya University of Medical Sciences, Osaka, Japan
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Kazunobu Okazaki;
Kazunobu Okazaki
‡Department of Environmental Physiology for Exercise, Osaka City University Graduate School of Medicine, Osaka, Japan
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Damian M. Bailey;
Damian M. Bailey
§Neurovascular Research Laboratory, Faculty of Health, Science and Sport, University of Glamorgan, Glamorgan, UK
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Tadayoshi Miyamoto
Tadayoshi Miyamoto
†Morinomiya University of Medical Sciences, Osaka, Japan
∥Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka, Japan
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Publisher: Portland Press Ltd
Received:
June 20 2012
Revision Received:
January 03 2013
Accepted:
January 21 2013
Accepted Manuscript online:
January 21 2013
Online ISSN: 1470-8736
Print ISSN: 0143-5221
© The Authors Journal compilation © 2013 Biochemical Society
2013
Clin Sci (Lond) (2013) 125 (1): 37–44.
Article history
Received:
June 20 2012
Revision Received:
January 03 2013
Accepted:
January 21 2013
Accepted Manuscript online:
January 21 2013
Citation
Shigehiko Ogoh, Hidehiro Nakahara, Kazunobu Okazaki, Damian M. Bailey, Tadayoshi Miyamoto; Cerebral hypoperfusion modifies the respiratory chemoreflex during orthostatic stress. Clin Sci (Lond) 1 July 2013; 125 (1): 37–44. doi: https://doi.org/10.1042/CS201200335
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