From the Totman Laboratory for Cerebrovascular Research, Department of
Pharmacology, College of Medicine, University of Vermont, Burlington.
Correspondence to John A. Bevan, MD, Department of Pharmacology, University of Vermont, Given Building, Burlington, VT 05405-0068.
Background and Purpose—Pressure and
shear stress exerted by flowing blood are two mechanical forces that
play a major role in the regulation of vascular tone. We
sought to evaluate the interaction between pressure and flow in
isolated rabbit cerebral arteries.
Methods—Responses to intraluminal flow of isolated pressurized
rabbit posterior cerebral arteries were investigated at low, medium,
and high levels of myogenic tone by setting the luminal pressure at 40,
60, and 80 mm Hg, respectively.
Results—At both low and medium levels of myogenic tone, flow
induced dilation. The response was significantly larger at 40 than at
60 mm Hg. At the high level of myogenic tone, the response to
flow consisted of a combination of an initial transient dilation
followed by sustained constriction. Flow-induced dilation but not
flow-induced constriction response was endothelium
dependent. Removal of the endothelium inhibited the
dilator response by
Conclusions—The intraluminal pressure and in consequence the
level of myogenic tone at which flow is applied determine the nature of
the response of the smooth muscle cells of the blood vessel wall.
Departments
of Physiology, Pharmacology, and Biochemistry,
Center for Perinatal Biology,
Loma Linda University School of Medicine,
Loma Linda, Calif
© 1998 American Heart Association, Inc.
Original Contributions
High Levels of Myogenic Tone Antagonize the Dilator Response to Flow of Small Rabbit Cerebral Arteries
80%. Flow-induced dilation was inhibited
(40%) by
N
-nitro-L-arginine (100
µmol/L) but not by indomethacin (10 µmol/L).
Endothelium removal not only decreased the amplitude of
flow-induced dilation but also promoted the appearance of flow-induced
constriction at low and medium levels of myogenic tone.
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