AJP - Heart and Circulatory Physiology, Vol 257, Issue 2 590-H596, Copyright © 1989 by American Physiological Society
Effects of reflex stimuli on blood flow to the adrenal medulla
F. M. Faraci, W. M. Chilian, J. K. Williams and D. D. Heistad
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
The goal of this study was to examine changes in blood flow to the adrenal
medulla during reflex stimuli that release catecholamines. Adrenal blood
flow was measured with microspheres during exercise in conscious dogs and
during bicuculline-induced seizures in anesthetized dogs. In awake dogs,
blood flow to the adrenal cortex and adrenal medulla was 310 +/- 48 and
1,613 +/- 258 (SE) ml.min-1.100 g-1, respectively. Blood flow to the cortex
and medulla was not affected by moderate exercise. Anesthesia
(pentobarbital sodium) reduced blood flow to the adrenal cortex and medulla
to 158 +/- 12 and 243 +/- 24 ml.min-1.100 g-1, respectively. In
anesthetized dogs, seizures markedly increased blood flow to the adrenal
medulla (282 +/- 68 to 1,257 +/- 128 ml.min-1.100 g-1), and this response
was blocked by sectioning the greater splanchnic nerve. Vasodilator
responses of the adrenal medulla to adenosine were not impaired by adrenal
denervation. Blood flow to the adrenal cortex was not affected by seizures
but increased in response to intravenous adenosine. These findings suggest
that 1) anesthesia decreases adrenal blood flow, particularly to the
adrenal medulla, and 2) reflex stimuli that release catecholamines can
produce selective increases in blood flow to the adrenal medulla.
