AJP - Heart and Circulatory Physiology, Vol 244, Issue 3 437-H443, Copyright © 1983 by American Physiological Society
Reflex modulation of carotid sinus baroreceptor activity in the dog
R. B. Felder, C. M. Heesch and M. D. Thames
Carotid sinus baroreceptor (CBR) sensitivity may be increased by electrical
stimulation of sympathetic nerves passing to the carotid sinus region. It
remains unknown if reflexly induced changes in efferent sympathetic
discharge affect CBR function. In 17 anesthetized dogs, we reflexly induced
alterations in sympathetic discharge and recorded CBR activity originating
from a vascularly isolated carotid sinus. The stimulus to the baroreceptors
was pulsatile with constant mean and pulse pressure. Occlusion of the
contralateral common carotid artery (n = 6) resulted in a reflex increase
in arterial pressure (116 +/- 10 to 153 +/- 14 mmHg) and an increase (121
+/- 2% of control) in baroreceptor activity (P less than 0.05). Inferior
vena caval occlusion (n = 6), which induced a reduction in arterial
pressure (145 +/- 19 to 75 +/- 21 mmHg), also provoked an increase (141 +/-
10% of control) in baroreceptor discharge (P less than 0.05). Raising
pressure (to 200 mmHg) in the contralateral carotid sinus (n = 7) resulted
in a reflex decrease in arterial pressure (169 +/- 16 to 129 +/- 13 mmHg)
and a reduction (82 +/- 3% of control) in baroreceptor activity (P less
than 0.05). The changes in baroreceptor discharge were abolished by
ipsilateral cervical sympathectomy or ganglionic blockade (n = 4). Our
findings demonstrate that reflexly induced alterations in the activity of
sympathetic fibers innervating the carotid sinuses can modulate
baroreceptor discharge.
