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Evaluation of Cerebral Blood Flow Autoregulation in the Rat Using Laser Doppler Flowmetry
Published on: January 19, 2020
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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
Summary
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.
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