AJP - Heart and Circulatory Physiology, Vol 256, Issue 4 999-1005, Copyright © 1989 by American Physiological Society

ARTICLES

PGE2 and arachidonate inhibit the baroreflex in conscious dogs via cardiac receptors

M. J. Panzenbeck, W. Tan, M. A. Hajdu, K. G. Cornish and I. H. Zucker
Department of Physiology and Biophysics, University of Nebraska College of Medicine, Omaha 68105.

Prostaglandin (PG) I2 and PGE2 are known to stimulate left ventricular receptors with nonmyelinated vagal afferents. The present experiments were performed to determine the effects of intracoronary infusion of PGE2 (10-50 ng.kg-1.min-1) and arachidonic acid (50-100 micrograms.kg-1.min-1) on the baroreflex control of heart rate in conscious dogs. Dogs were anesthetized with pentobarbital sodium and were instrumented using sterile surgical techniques. After recovery, baroreflex pressure-heart rate curves were constructed by varying arterial pressure with partial occlusions of the descending aorta or inferior vena cava. Intracoronary infusion of PGE2 significantly inhibited the maximum heart rate achieved during unloading of baroreceptors, attenuated the heart rate range, and decreased the maximum slope of the baroreflex curve; PGE2 had no significant effect on the minimum heart rate during hypertension. Intravenous infusion of PGE2 did not cause significant baroreflex inhibition, and pericoronary nerve block in three dogs prevented the effects of intracoronary PGE2. Intracoronary infusion of arachidonic acid had effects on the baroreflex control of heart rate similar to those of PGE2. The effects of arachidonic acid infusion were prevented by cyclooxygenase blockade. Thus intracoronary PGE2 and arachidonic acid inhibit the baroreflex control of heart rate most likely via stimulation of left ventricular receptors with vagal C-fiber afferents. The effects of arachidonic acid were secondary to synthesis of prostaglandins.

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