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Comparative Study
. 2010 Jan;41(1):102-9.
doi: 10.1161/STROKEAHA.109.557132. Epub 2009 Dec 10.

Sympathetic control of the cerebral vasculature in humans

J W Hamner  1 , Can Ozan Tan, Kichang Lee, Michael A Cohen, J Andrew Taylor
Affiliations
Comparative Study

Sympathetic control of the cerebral vasculature in humans

J W Hamner et al. Stroke. 2010 Jan.

Abstract

Background and purpose: The role of the sympathetic nervous system in cerebral autoregulation remains poorly characterized. We examined cerebral blood flow responses to augmented arterial pressure oscillations with and without sympathetic blockade and compared them with responses in the forearm circulation.

Methods: An oscillatory lower body negative pressure of 40 mm Hg was used at 6 frequencies from 0.03 to 0.08 Hz in 11 healthy subjects with and without alpha-adrenergic blockade by phentolamine.

Results: Sympathetic blockade resulted in unchanged mean pressure and cerebral flow. The transfer function relationship to arterial pressure at frequencies >0.05 Hz was significantly increased in both the cerebral and brachial circulations, but the coherence of the relation remained weak at the lowest frequencies in the cerebral circulation.

Conclusions: Our data demonstrate a strong, frequency-dependent role for sympathetic regulation of blood flow in both cerebral and brachial circulations. However, marked differences in the response to blockade suggest the control of the cerebral circulation at longer time scales is characterized by important nonlinearities and relies on regulatory mechanisms other than the sympathetic system.

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Conflict of interest statement

Conflicts of Interest

There are no conflicts of interests.

Figures

Figure 1
Figure 1
Hemodynamic response to OLBNP in a representative subject at baseline.
Figure 2
Figure 2
Change in spectral density with sympathetic blockade.
Figure 3
Figure 3
Effect of sympathetic blockade on pressure and flow at 0.03 Hz OLBNP in a representative subject.
Figure 4
Figure 4
Coherence and gain between pressure and flow in the middle cerebral and brachial arteries with and without sympathetic blockade. Freq: Frequency, Cond: Condition, Freq × Cond: Frequency and condition interaction term. * p<0.05 vs. baseline at the OLBNP frequency.
See this image and copyright information in PMC

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