Spatiotemporal aspects of sympathetic c-fiber afferent activity in
the pressor reflex during abdominal ischemia.
Pan, Hui-Lin, Zachary B. Zeisse, Koullis F. Pitsillides, and John C.
Longhurst.
Division of Cardiovascular Medicine, Departments of Internal
Medicine and Human Physiology, University of California School of
Medicine, Davis, California 95616 and Departments of Anesthesia,
Physiology and Pharmacology, Bowman Gray School of Medicine, Wake
Forest University, Winston-Salem, North Carolina 27157
APStracts 3:0543H, 1996.
Activation of abdominal sympathetic visceral afferents during ischemia
elicits excitatory cardiovascular reflexes. The present study
examined the time course and discharge patterns of activation of
ischemically sensitive sympathetic C-fiber afferents, then determined
the relationship between summated afferent activity and the pressor
reflex induced by prolonged abdominal ischemia. Single-unit activity
of abdominal C-fiber afferents was recorded from the right thoracic
sympathetic chain of anesthetized cats during 30 min of ischemia. The
reflex pressor response to abdominal ischemia was induced by
occlusion of celiac and superior mesenteric arteries. Of 68 C-fiber
afferents studied, 36 (53%) were activated during 30 min of ischemia
while the activity of remaining 32 were not altered. Onset latencies
of 36 C-fiber afferents activated by ischemia ranged from 1.0 to 17.4
min with an average of 6.1+/-0.8 min. The majority of activated
afferents manifested a bursting pattern of discharge activity as
ischemia was prolonged beyond 10 min. Summated response of activated
afferents, but not individual afferent activity, was related closely
to the reflex pressor response during 30 min of ischemia. These
results suggest that both recruitment of sufficient numbers of C
-fiber afferents and adequate discharge frequency of afferents
constitute an encoding mechanism for the pressor reflex during
abdominal ischemia.
Received 21 June 1996; accepted in final form 18 November 1996.
APS Manuscript Number H557-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996