AJP - Heart and Circulatory Physiology, Vol 244, Issue 2 194-H200, Copyright © 1983 by American Physiological Society
Arterial baroreceptors have minimal physiological effects on adrenal medullary secretion
D. C. Fater, W. D. Sundet, H. D. Schultz and K. L. Goetz
The influence of arterial baroreceptors on secretion of catecholamines from
the adrenal medulla was evaluated by several methods. Conscious mongrel
dogs with surgically denervated hearts were hemorrhaged until an estimated
16% of their blood volume had been removed. On a separate day they were
anesthetized and their blood pressure was lowered with intravenous
nitroglycerin. Neither of these maneuvers produced appreciable increases in
heart rate in these dogs. In contrast, in a group of sham-operated control
dogs, hemorrhage induced a mean increase in heart rate of 20 beats/min (P
less than 0.05), and nitroglycerin-induced hypotension induced an increase
of 50 beats/min (P less than 0.05). In a separate group of conscious dogs
with aortic arch denervation but intact cardiac nerves, occlusion of the
common carotid arteries for 5 min increased blood pressure and heart rate
significantly but elicited only small, insignificant increases in plasma
epinephrine and norepinephrine; the peak concentration of epinephrine
achieved was considerably less than the amount necessary to cause
appreciable effects on blood pressure and heart rate as determined in
another experiment by infusing varying amounts of epinephrine into
conscious, cardiac-denervated dogs. We conclude that the arterial
baroreceptor reflex, within the range of activity likely to occur during
most physiological and pathophysiological adjustments in the conscious dog,
exerts only minimal effects on the secretion of catecholamines from the
adrenal medulla.
