Role of summation of afferent input in cardiovascular reflexes from
splanchnic nerve stimulation.
Pan, Hui-Lin, Zachary B. Zeisse, and John C. Longhurst.
Division of Cardiovascular Medicine, Departments of Internal
Medicine and Human Physiology, University of California, Davis,
Davis, California 95616
APStracts 2:0340H, 1995.
Stimulation of abdominal sympathetic visceral afferents reflexly
excites the cardiovascular system. The present study examined the
role of summation of afferent input in this reflex. Single-unit
activity of A[delta]- and C-fiber afferents was recorded from the
right thoracic sympathetic chain in anesthetized cats to determine
the relationship between intensities of electrical stimulation and
the types of nerve fibers within the right greater splanchnic nerve.
The differential effect of cooling on A[delta]- and C-fiber axons in
the sympathetic chain also was examined by recording single-unit
afferent activity. Reflex cardiovascular responses were induced by
electrical stimulation of the central cut end of the right greater
splanchnic nerve. We observed that the numbers of A[delta]- and C
-fibers activated by electrical stimulation were proportional to the
intensity of stimulation. However, neither local cooling nor
intensity of stimulation provided a means to separate A[delta]- and
C-fibers contained in the sympathetic chain. The results demonstrate
that the magnitude of excitatory cardiovascular reflexes is frequency
dependent and is related directly to intensity of electrical
stimulation, suggesting that both adequate discharge frequency of the
afferent and sufficient numbers of afferents recruited are crucial
factors for full expression of reflex cardiovascular responses.
Received 8 June 1995; accepted in final form 4 August 1995.
APS Manuscript Number H526-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.