AJP - Heart and Circulatory Physiology, Vol 248, Issue 4 485-H492, Copyright © 1985 by American Physiological Society
Chronic norepinephrine infusion and adrenergic function of hypertrophied hearts
F. M. Siri
The ability of chronic subpressor norepinephrine infusion to prevent
depletion of myocardial norepinephrine stores and deterioration of
myocardial adrenergic nerve function in congestive heart failure was
examined. Four groups of adult male Wistar rats were subjected to aortic
constriction or sham aortic constriction, along with either norepinephrine
infusion or infusion of vehicle alone. After 7 days of treatment, these
animals were evaluated for myocardial norepinephrine content, ventricular
mass, and resting hemodynamics. Chronotropic and inotropic responses to
electrical stimulation of the left and right cervical sympathetic trunks
and to intravenous injections of tyramine and norepinephrine were measured.
Chronic norepinephrine infusion normalized myocardial norepinephrine
content in aortic-constricted rats but did not significantly affect heart
size or mortality. Norepinephrine infusion diminished responses to
sympathetic nerve stimulation, despite apparently normal myocardial
norepinephrine sensitivity. The results suggest that chronic norepinephrine
infusion suppresses neurotransmission in the heart by some means unrelated
to its norepinephrine store. This suppression may be compensatory and
reversible.
