AJP - Regulatory, Integrative and Comparative Physiology, Vol 247, Issue 2 237-R245, Copyright © 1984 by American Physiological Society
Intracoronary epinephrine attenuates baroreflex control of heart rate in the conscious dog
M. J. Holmberg, A. J. Gorman, K. G. Cornish and I. H. Zucker
In the present study, the reflex effects of low-dose (12.5-50 ng X kg-1 X
min-1) intracoronary epinephrine infusion on the arterial baroreflex
control of heart rate were studied. Mean arterial blood pressure-heart rate
curves were constructed by changing mean arterial blood pressure with
graded occlusions of the descending aorta and inferior vena cava.
Intracoronary epinephrine increased left ventricular dP/dtmax by an average
of 309 +/- 67.0 mmHg/s but did not alter resting mean arterial blood
pressure or heart rate. Peak sensitivity, the maximum absolute slope along
the mean arterial blood pressure-heart rate curve, and heart rate range
were 32.7 +/- 3.2 and 26.7 +/- 2.5% less during intracoronary epinephrine
compared with control, respectively. Intracoronary epinephrine did not
alter the median, threshold, or saturation pressure of the mean arterial
blood pressure-heart rate curve. Lidocaine block of the pericoronary
nerves, which blocked the ventricular afferent pathway, eliminated the
effects of intracoronary epinephrine on the arterial baroreflex. Atropine
abolished the effects of intracoronary epinephrine on arterial baroreflex
control of heart rate. We conclude that intracoronary epinephrine reflexly
attenuates the arterial baroreflex control of heart rate in the conscious
dog through activation of ventricular receptors. This response is mediated
by cardiac parasympathetic efferents common to both reflex arcs.
