Journal of Applied Physiology, Vol 38, Issue 1 1-4, Copyright © 1975 by American Physiological Society
Enhanced carotid sinus baroreflex responses in dogs with chronic A-V block
J. DiSalvo, R. Reynolds, J. L. Robinson and G. Grupp
Effects of carotid sinus pressure on arterial pressure, atrial rate, and
ventricular rate were examined in anesthetized normal dogs and in dogs with
chronic complete A-V block. Change in arterial pressure per mmHg change in
sinus pressure was 0.8 plus or minus 0.2 mmHg for controls but increased (P
is less than 0.001) to 1.6 plus or minus 0.1 mmHg in A-V blocked dogs.
Arterial pressure was 140-145 mmHg at low sinus pressure in both groups,
but at high sinus pressure arterial pressure was significantly lower in A-V
blocked dogs (44 plus or minus 4 mmHg) than in controls (92 plus or minus 8
mmHg). These differences were virtually abolished after vagotomy. Heart
rate increased in normal dogs as sinus pressure was increased before
vagotomy, but decreased after vagotomy. In blocked dogs atrial and
ventricular rates decreased at high sinus pressure either before or after
vagotomy. The results show that reflex circulatory responses to changes in
carotid sinus pressure are enhanced in dogs with A-V block. This
enhancement may involve attenuation of buffering influences exerted from
other baroreceptors whose afferents are in the vagus nerves.
