Impact of development and chronic hypoxia on norepinephrine release
from adrenergic nerves in sheep arteries.
Buchholz, John, Kim Edwards-Teunissen, and Sue P. Duckles.
1Department of Pharmacology and Physiology, Loma Linda University,
School of Medicine, Loma Linda, CA 92350; 2Catholic University of
Nijmegen, Sophiaweg 104 6523 NJ Nijmegen, The Netherlands;
3Department of Pharmacology, College of Medicine, University of
California, Irvine, CA 92697.
APStracts 5:0453R, 1998.
Buchholz, John, Kim Edwards-Teunissen and Sue P. Duckles. Impact of
development and chronic hypoxia on norepinephrine release from
adrenergic nerves in sheep arteries.-- To examine effects of
development and chronic high altitude hypoxia on sympathetic nerve
function in sheep, norepinephrine release was measured in vitro from
middle cerebral and facial arteries. Capsaicin was used to test the
role of capsaicin-sensitive sensory nerves; norepinephrine release
was not altered by capsaicin treatment. Nw -nitro-L-arginine methyl
ester (L-NAME), an inhibitor of NO synthase, decreased stimulation
-evoked norepinephrine release in middle cerebral arteries from
normoxic sheep with no effect in hypoxic arteries or facial arteries.
Thus NO releasing nerves augmented norepinephrine release.
Furthermore, the function of NO releasing nerves declined after
chronic hypoxia. Despite loss of the augmenting effects of NO,
stimulation-evoked fractional norepinephrine release was unchanged
after chronic hypoxia suggesting that middle cerebral arteries adapt
to hypoxia by increasing stimulation-evoked norepinephrine release.
In fetal facial arteries chronic hypoxia resulted in a decline in
stimulation-evoked norepinephrine release, but there was an increase
in the adult facial artery. In the adult adaptation to chronic
hypoxia is similar in both cerebral and facial arteries. However,
differential adaptation in fetal adrenergic nerves may reflect
differences in fetal redistribution of blood flow in the face of
chronic hypoxia but could also possibly contribute to increased
incidence of fetal morbidity.
Received 8 May 1998; accepted in final form 23 November 1998.
APS Manuscript Number R293-8.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 9 December 1998