Título :	Neurovascular coupling is not influenced by lower body negative pressure in humans
Autor :	Samora, Milena Vianna, Lauro Casqueiro Carmo, Jake C. Macedo, Victor Dawes, Matthew Phillips, Aaron A. Paton, Julian F. R. Fisher, James P.
metadata.dc.identifier.orcid:	https://orcid.org/0000-0001-6348-1786 https://orcid.org/0000-0002-5747-0295 https://orcid.org/0000-0001-7851-9222
Assunto::	Circulação cerebral Acoplamento neurovascular Sistema nervoso simpático
Fecha de publicación :	2020
Editorial :	American Physiological Society
Citación :	SAMORA, Milena et al. Neurovascular coupling is not influenced by lower body negative pressure in humans. American journal of physiology-heart and circulatory physiology, v. 319, n. 1, H22-H31, 2020. DOI: https://doi.org/10.1152/ajpheart.00076.2020.
Abstract:	Cerebral blood flow is tightly coupled with local neuronal activation and metabolism, i.e., neurovascular coupling (NVC). Studies suggest a role of sympathetic nervous system in the regulation of cerebral blood flow. However, this is controversial, and the sympathetic regulation of NVC in humans remains unclear. Since impaired NVC has been identified in several chronic diseases associated with a heightened sympathetic activity, we aimed to determine whether reflex-mediated sympathetic activation via lower body negative pressure (LBNP) attenuates NVC in humans. NVC was assessed using a visual stimulation protocol (5 cycles of 30 s eyes closed and 30 s of reading) in 11 healthy participants (aged 24 ± 3 yr). NVC assessments were made under control conditions and during LBNP at -20 and -40 mmHg. Posterior (PCA) and middle (MCA) cerebral artery mean blood velocity (Vmean) and vertebral artery blood flow (VAflow) were simultaneously determined with cardiorespiratory variables. Under control conditions, the visual stimulation evoked a robust increase in PCAVmean (∆18.0 ± 4.5%), a moderate rise in VAflow (∆9.6 ± 4.3%), and a modest increase in MCAVmean (∆3.0 ± 1.9%). The magnitude of NVC response was not affected by mild-to-moderate LBNP (all P > 0.05 for repeated-measures ANOVA). Given the small change that occurred in partial pressure of end-tidal CO2 during LBNP, this hypocapnia condition was matched via voluntary hyperventilation in absence of LBNP in a subgroup of participants (n=8). The mild hypocapnia during LBNP did not exert a confounding influence on the NVC response. These findings indicate that the NVC is not influenced by LBNP or mild hypocapnia in humans.
metadata.dc.description.unidade:	Faculdade de Educação Física (FEF)
DOI:	https://doi.org/10.1152/ajpheart.00076.2020
metadata.dc.relation.publisherversion:	https://journals.physiology.org/doi/abs/10.1152/ajpheart.00076.2020
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