Cerebral vasoreactivity during hypercapnia is reset by augmented sympathetic influence

Peizhen Zhang, Guoyuan Huang, Xiangrong Shi

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Abstract

Sympathetic nerve activity influences cerebral blood flow, but it is unknown whether augmented sympathetic nerve activity resets cerebral vasoreactivity to hypercapnia. This study tested the hypothesis that cerebral vasodilation during hypercapnia is restrained by lower-body negative pressure (LBNP)-stimulated sympathoexcitation. Cerebral hemodynamic responses were assessed in nine healthy volunteers [age 25 yr (SD 3)] during rebreathing-induced increases in partial pressure of end-tidal CO2 (PETCO2) at rest and during LBNP. Cerebral hemodynamic responses were determined by changes in flow velocity of middle cerebral artery (MCAV) using transcranial Doppler sonography and in regional cerebral tissue oxygenation (ScO2) using near-infrared spectroscopy. PETCO2 values during rebreathing were similarly increased from 41.9 to 56.5 mmHg at rest and from 40.7 to 56.0 mmHg during LBNP of - 15 Torr. However, the rates of increases in MCAV and in ScO2 per unit increase in PETCO2 (i.e., the slopes of MCAV/PETCO2 and ScO2/PETCO2) were significantly (P ≤0.05) decreased from 2.62 ± 0.16 cm·s -1·mmHg-1 and 0.89 ± 0.10%/mmHg at rest to 1.68 ± 0.18 cm·s-1·mmHg-1 and 0.63 ± 0.07%/mmHg during LBNP. In conclusion, the sensitivity of cerebral vasoreactivity to hypercapnia, in terms of the rate of increases in MCAV and in ScO2, is diminished by LBNP-stimulated sympathoexcitation.

Original languageEnglish
Pages (from-to)352-358
Number of pages7
JournalJournal of Applied Physiology
Volume110
Issue number2
DOIs
StatePublished - 1 Feb 2011

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Lower Body Negative Pressure
Hypercapnia
Pressure
Cerebrovascular Circulation
Hemodynamics
Doppler Transcranial Ultrasonography
Near-Infrared Spectroscopy
Partial Pressure
Middle Cerebral Artery
Vasodilation
Healthy Volunteers

Cite this

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title = "Cerebral vasoreactivity during hypercapnia is reset by augmented sympathetic influence",
abstract = "Sympathetic nerve activity influences cerebral blood flow, but it is unknown whether augmented sympathetic nerve activity resets cerebral vasoreactivity to hypercapnia. This study tested the hypothesis that cerebral vasodilation during hypercapnia is restrained by lower-body negative pressure (LBNP)-stimulated sympathoexcitation. Cerebral hemodynamic responses were assessed in nine healthy volunteers [age 25 yr (SD 3)] during rebreathing-induced increases in partial pressure of end-tidal CO2 (PETCO2) at rest and during LBNP. Cerebral hemodynamic responses were determined by changes in flow velocity of middle cerebral artery (MCAV) using transcranial Doppler sonography and in regional cerebral tissue oxygenation (ScO2) using near-infrared spectroscopy. PETCO2 values during rebreathing were similarly increased from 41.9 to 56.5 mmHg at rest and from 40.7 to 56.0 mmHg during LBNP of - 15 Torr. However, the rates of increases in MCAV and in ScO2 per unit increase in PETCO2 (i.e., the slopes of MCAV/PETCO2 and ScO2/PETCO2) were significantly (P ≤0.05) decreased from 2.62 ± 0.16 cm·s -1·mmHg-1 and 0.89 ± 0.10{\%}/mmHg at rest to 1.68 ± 0.18 cm·s-1·mmHg-1 and 0.63 ± 0.07{\%}/mmHg during LBNP. In conclusion, the sensitivity of cerebral vasoreactivity to hypercapnia, in terms of the rate of increases in MCAV and in ScO2, is diminished by LBNP-stimulated sympathoexcitation.",
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Cerebral vasoreactivity during hypercapnia is reset by augmented sympathetic influence. / Zhang, Peizhen; Huang, Guoyuan; Shi, Xiangrong.

In: Journal of Applied Physiology, Vol. 110, No. 2, 01.02.2011, p. 352-358.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Cerebral vasoreactivity during hypercapnia is reset by augmented sympathetic influence

AU - Zhang, Peizhen

AU - Huang, Guoyuan

AU - Shi, Xiangrong

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N2 - Sympathetic nerve activity influences cerebral blood flow, but it is unknown whether augmented sympathetic nerve activity resets cerebral vasoreactivity to hypercapnia. This study tested the hypothesis that cerebral vasodilation during hypercapnia is restrained by lower-body negative pressure (LBNP)-stimulated sympathoexcitation. Cerebral hemodynamic responses were assessed in nine healthy volunteers [age 25 yr (SD 3)] during rebreathing-induced increases in partial pressure of end-tidal CO2 (PETCO2) at rest and during LBNP. Cerebral hemodynamic responses were determined by changes in flow velocity of middle cerebral artery (MCAV) using transcranial Doppler sonography and in regional cerebral tissue oxygenation (ScO2) using near-infrared spectroscopy. PETCO2 values during rebreathing were similarly increased from 41.9 to 56.5 mmHg at rest and from 40.7 to 56.0 mmHg during LBNP of - 15 Torr. However, the rates of increases in MCAV and in ScO2 per unit increase in PETCO2 (i.e., the slopes of MCAV/PETCO2 and ScO2/PETCO2) were significantly (P ≤0.05) decreased from 2.62 ± 0.16 cm·s -1·mmHg-1 and 0.89 ± 0.10%/mmHg at rest to 1.68 ± 0.18 cm·s-1·mmHg-1 and 0.63 ± 0.07%/mmHg during LBNP. In conclusion, the sensitivity of cerebral vasoreactivity to hypercapnia, in terms of the rate of increases in MCAV and in ScO2, is diminished by LBNP-stimulated sympathoexcitation.

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