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Dynamic cerebral autoregulation is unrelated to decrease in external carotid artery blood flow during acute

Shigehiko Ogoh1, Henrik Sørensen2, Ai Hirasawa3

  • 1Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan.

Experimental Physiology
|May 28, 2016
PubMed

Insights

Sympathetic blockade impairs dynamic cerebral autoregulation (CA). This study found that α1-receptor blockade delayed internal carotid artery blood flow recovery during hypotension, but external carotid artery vasoconstriction did not change, suggesting ECA does not influence dynamic CA.

Area of Science:

  • Neuroscience
  • Physiology
  • Cardiovascular Research

Background:

  • Dynamic cerebral autoregulation (CA) is crucial for maintaining stable brain blood flow.
  • Sympathetic blockade is known to impair CA.
  • The external carotid artery (ECA) vascular bed's role in regulating internal carotid artery (ICA) blood flow during CA is not fully understood.

Purpose of the Study:

  • To investigate whether α1-receptor blockade-induced impairment of dynamic CA is linked to reduced vasoconstriction in the ECA.
  • To determine if ECA vasoconstriction influences the recovery of ICA blood flow during acute hypotension.

Main Methods:

  • Nine healthy young men underwent induced acute hypotension via thigh-cuff release.
  • Internal carotid artery (ICA) and external carotid artery (ECA) blood flow were measured using duplex ultrasound.
  • The α1-receptor blocker prazosin was administered, and its effects on dynamic CA and blood flow responses were analyzed.

Main Results:

  • α1-receptor blockade attenuated dynamic CA, delaying ICA blood flow recovery during hypotension.
  • Contrary to the hypothesis, ECA blood flow response to acute hypotension was not affected by prazosin.
  • Mean arterial pressure reduction was similar in both control and prazosin conditions.

Conclusions:

  • The α1-receptor blockade-induced impairment of dynamic CA is independent of changes in ECA vasoconstriction.
  • ECA vasoconstriction does not appear to play a significant role in defending ICA blood flow during acute hypotension.
  • The sympathetic nervous system, via the ECA vascular bed, does not contribute to dynamic CA under these experimental conditions.
Abstract

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