AJP - Regulatory, Integrative and Comparative Physiology, Vol 262, Issue 5 872-R878, Copyright © 1992 by American Physiological Society
Identification of carotid vascular receptors that control adrenal catecholamine secretion in dogs
W. C. Engeland, C. D. Zippe and D. S. Gann
Department of Surgery, Brown University, Rhode Island Hospital, Providence 02903.
The role of carotid sinus and thyrocarotid mechanoreceptors in the reflex
control of adrenal medullary function was assessed in anesthetized dogs
with adrenal vein catheters. Dogs underwent carotid sinus, thyrocarotid
junction, combined carotid sinus and thyrocarotid junction, or sham
denervation. On the day after surgery, catecholamine secretion was measured
after carotid occlusion proximal to the thyrocarotid junction, cervical
vagotomy, and repeat carotid occlusion, each separated by 90 min. After
combined carotid denervation, baseline norepinephrine secretion was
increased, resulting in a decreased epinephrine-to-norepinephrine ratio.
Carotid occlusion before vagotomy did not change the secretion of
catecholamines or the epinephrine-to-norepinephrine ratio. After sham
carotid denervation, acute vagotomy did not affect catecholamine secretion.
However, after denervation of the carotid sinus or thyrocarotid junction,
vagotomy resulted in small increases in catecholamine secretion without
changing the epinephrine-to-norepinephrine ratio; the magnitude of the
response was augmented after combined denervation. At 90 min after vagotomy
in dogs with intact carotid baroreceptors, carotid occlusion increased
adrenal secretion of catecholamines and decreased the
epinephrine-to-norepinephrine ratio. After denervation of carotid sinus or
thyrocarotid junction receptors, carotid occlusion increased secretion of
catecholamines without changing the epinephrine-to-norepinephrine ratio;
the response was abolished by combined denervation. These results show that
both carotid sinus and thyrocarotid receptors contribute to the
adrenomedullary response to carotid occlusion and to acute vagotomy. Also,
reduction in the activity of carotid sinus and thyrocarotid junction
receptors chronically (by denervation) or acutely (by carotid occlusion)
results in preferential secretion of norepinephrine over epinephrine.
