AJP - Heart and Circulatory Physiology, Vol 248, Issue 6 930-H936, Copyright © 1985 by American Physiological Society
Reflex cardiovascular effects of intracoronary acetylstrophanthidin in the conscious dog
K. W. Barron and V. S. Bishop
The present experiments were designed to examine the reflex cardiovascular
effects of intracoronary administration of acetylstrophanthidin in the
conscious dog. Administration of 4 micrograms/kg of this agent into the
left circumflex coronary artery increased left ventricular dP/dtmax but had
no effect on mean arterial pressure, heart rate, renal resistance, or iliac
resistance. The positive inotropic effects of acetylstrophanthidin were
less under control conditions (+599 mmHg/s) than during bilateral cervical
vagal cold block (+850 mmHg/s, P less than 0.05); however, interruption of
vagal efferent influences (atropine) alone did not alter the contractile
effects of acetylstrophanthidin. Interruption of sympathetic efferent
influences on the heart with either the nicotinic ganglionic receptor
antagonist, hexamethonium, or the beta 1-adrenergic receptor antagonist,
metoprolol, also augmented the inotropic effects of acetylstrophanthidin to
a degree similar to that observed with vagal cold block. In contrast to the
effects observed with acetylstrophanthidin, the inotropic effects of
intracoronary administration of calcium gluconate were not altered by vagal
cold block or any other conditions examined in this study. We conclude that
interruption of vagal afferents results in an augmentation of the positive
inotropic actions of acetylstrophanthidin and that this augmented inotropic
effect can be accounted for by interruption of cardiac vagal
afferent-mediated restraint on sympathetic outflow to the heart.
