AJP - Heart and Circulatory Physiology, Vol 248, Issue 5 631-H636, Copyright © 1985 by American Physiological Society
Interaction of left atrial receptors and carotid sinus baroreceptors on heart rate in the dog
K. K. Teo, G. C. Man and C. T. Kappagoda
This study was undertaken to determine the influence of 1) the left atrial
receptors (LA) on the ability of the carotid sinus baroreceptors (CS) to
regulate heart rate and 2) the CS on the reflex increase in heart rate
mediated by the LA. The LA were stimulated by stretching the pulmonary
vein-atrial junctions in dogs anesthetized with alpha-chloralose. Aortic
pressure was controlled, and the pressure in the CS was regulated.
Stimulus-response curves were obtained relating heart rate to pressures in
the CS, in the control state, and during stimulation of LA (6 dogs).
Factorial analysis revealed that LA exerted a significant influence on
heart rate (P less than 0.01). Next the CS pressure was set at mid, low,
and high levels and the LA stimulated. It was found that the effect on
heart rate was greatest at the mid setting (+19.3 +/- 2.9 beats/min) and
least at the low setting of the pressure in the CS (+0.9 +/- 0.5, 11 dogs).
Sympathetic blockade attenuated significantly the response in the mid
setting of the CS pressure and left intact the response at the high setting
of the pressure in the CS. It is concluded that there is a significant
interaction between these two reflexes.
