AJP - Heart and Circulatory Physiology, Vol 242, Issue 2 148-H153, Copyright © 1982 by American Physiological Society
Responses to activation of cardiac sympathetic afferents with epicardial bradykinin
R. B. Felder and M. D. Thames
The cardiovascular reflex responses mediated by cardiac sympathetic
afferent fibers (CSA) appear to differ depending on the nature of the
activating stimulus. Although electrical stimulation of CSA may result in
either excitatory of inhibitory reflex responses in both cats and dogs,
topical application of bradykinin to these sensory endings elicits only
excitatory reflex responses in cats. The present experiments were performed
to determine whether CSA activated by epicardial bradykinin also mediate
solely excitatory reflex responses in the dog. The changes in efferent
cardiac or renal sympathetic nerve activity, mean arterial pressure, and
heart rate resulting from application of bradykinin to the left ventricular
epicardial surface were determined in 15 chloralose-anesthetized,
sinoaortic-denervated vagotomized dogs. Activation of CSA with bradykinin
(0.1--120 g/ml) elicited inhibitory responses in eight dogs, excitatory
responses in four dogs, and biphasic responses in three dogs. Both
excitatory and inhibitory reflexes were eliminated by cardiac sympathetic
afferent denervation. The results show that, in the dog, cardiac receptors
with sympathetic afferent fibers activated by epicardial bradykinin mediate
nonuniform reflex responses that tend to be predominantly inhibitory.
