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Effects of sympathetic nerves on cerebral blood flow in awake dogs
Journal article   Peer reviewed

Effects of sympathetic nerves on cerebral blood flow in awake dogs

Melvin L Marcus and Donald D Heistad
The American journal of physiology, Vol.236(4), pp.H549-H553
04/1979
DOI: 10.1152/ajpheart.1979.236.4.H549
PMID: 434219

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Abstract

Although cerebral blood vessels are densely innervated by sympathetic nerve fibers, the functional significance of the nerves is controversial. Because previous studies have been primarily performed in anesthetized animals, it is possible that failure to observe prominent neural control of the cerebral circulation was secondary to anesthetic-induced depression of the sympathetic nervous system. Therefore, we studied sympathetic control of the cerebral circulation in 11 awake chronically instrumented dogs. Total and regional cerebral blood flow was measured with 15-micrometer microspheres at control blood pressure and during three levels of progressive hemorrhagic hypotension. Sympathetic nerves had only a small effect (11% decrease; P less than 0.05) on flow to the cerebrum during moderate hypotension (mean arterial pressure 49 +/- 2 mmHg). Also, during severe hypotension, there was a bilateral redistribution of brain blood flow that tended to preserve flow to the medulla. Although these studies suggest that sympathetic nerves have a definite constrictor effect on cerebral vessels, the data support the concept that the functional importance of sympathetic nerves to cerebral vessels is limited.
Blood Pressure Microspheres Animals Sympathetic Nervous System - physiology Dogs Homeostasis Cerebrovascular Circulation Regional Blood Flow

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