AJP - Heart and Circulatory Physiology, Vol 253, Issue 1 47-H57, Copyright © 1987 by American Physiological Society
Nonuniformity of CBF response to NE- or ANG II-induced hypertension in rabbits
A. M. Reynier-Rebuffel, P. Aubineau, O. Issertial and J. Seylaz
The regional response of brain vasculature to moderate hypertension was
investigated using two hypertensive drugs, norepinephrine (NE) and
angiotensin II (ANG II), infused intravenously at low concentrations
(increase in blood pressure 15-40 mm Hg). Regional cerebral blood flow
(rCBF) was measured in unanesthetized and anesthetized rabbits using the
[14C]ethanol saturation technique. In both groups of animals, NE and ANG II
induced regional differences in the flow changes as compared with controls,
confirming a regional (or segmental) heterogeneity in the regulatory
mechanisms to hypertension. The responses to identical rises in blood
pressure (BP) in most of the structures analyzed depended on the drug used.
In the unanesthetized rabbits, the increase in vascular resistance induced
by NE was greater than that induced by ANG II. With the two drugs, there
was no correlation between the flow changes in any of the structures
considered and either the BP increase or the BP level in unanesthetized
animals. However, these flow changes were correlated with the BP increase
in anesthetized animals, although differences between the effects of NE and
ANG II were again observed. This study suggests that cerebrovascular
regulatory mechanisms in hypertension are probably more complex than a
simple myogenic reaction. Their heterogeneity and their dependence both on
the cause of hypertension and on the presence of anesthetics suggest the
intervention of an integrating pathway.
