AJP - Heart and Circulatory Physiology, Vol 256, Issue 2 493-H501, Copyright © 1989 by American Physiological Society
Mechanics and composition of arterioles in brain stem and cerebrum
G. L. Baumbach, J. E. Siems, F. M. Faraci and D. D. Heistad
Department of Pathology, University of Iowa College of Medicine, Iowa City.
The goal of this study was to compare mechanics and composition of
arterioles in brain stem and cerebrum. We calculated stress and strain of
pial arterioles in anesthetized rats from measurements of pial arteriolar
pressure (servo-null), diameter, and cross-sectional area of the vessel
wall. Composition of pial arterioles was quantitated using point-counting
stereology. Before deactivation of smooth muscle with
ethylenediaminetetraacetic acid (EDTA), pial arteriolar pressure and
diameter were 28 and 30% greater (P less than 0.05) in brain stem than
cerebrum. After EDTA, diameter of arterioles was similar in brain stem and
cerebrum. Cross-sectional area of the arteriolar wall was 32% greater (P
less than 0.05) in brain stem than cerebrum. Stress-strain curves indicated
that distensibility of pial arterioles is greater in brain stem than
cerebrum. The proportion of nondistensible (collagen and basement membrane)
to distensible (elastin, smooth muscle, and endothelium) components was 20%
less (P less than 0.05) in brain stem than cerebral arterioles. We conclude
that 1) cross-sectional area of the vessel wall in arterioles of comparable
size is greater in brain stem than cerebrum, 2) distensibility of
arterioles is greater in brain stem than cerebrum, despite greater
cross-sectional area of the arteriolar wall in brain stem, and 3) the
proportion of elastic components is greater in brain stem than cerebral
arterioles, which may contribute to greater arteriolar distensibility in
brain stem.
