Influence of intravenous saline infusion on the aortic baroreceptor and left atrial B-type receptor activity in dogs.

Influence of i.v. saline infusion on aortic arch pressure, left atrial mean pressure, heart rate, and the time-related characteristics of aortic arch baroreceptor and left atrial B-type receptor activities were studied in 20 beagle dogs. Saline infusion induced tachycardia in 10 dogs and bradycardia in 10. Aortic arch and left atrial pressures increased in both HR response groups. The average discharge rate of baroreceptors increased in both HR response groups, while the duration of baroreceptor burst, the number of baroreceptor action potentials/heart cycle and the average burst frequency did not increase significantly in the group that responded with tachycardia but increased significantly in the group that responded with bradycardia. The number of left atrial B-type action potentials/heart cycle, the average discharge rate and average burst frequency increased in both HR response groups. We conclude that the duration of baroreceptor burst, baroreceptor average burst frequency and the number of baroreceptor impulses/cardiac cycle are the important parameters eliciting baroreceptor reflex to i.v. saline infusion.