Time-related characteristics of aortic arch baroreceptor and left atrial B-type receptor activities

Influence of i.v. saline infusion on aortic arch pressure, mean left atrial 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 pressure increased equally in both heart rate response groups. The duration of baroreceptor activity increased in the group responding with bradycardia but stayed constant in the group responding with tachycardia. Changes in the duration of baroreceptor inactivity period significantly reflect changes in the duration of aortic diastole. It was concluded that from the duration of the baroreceptor inactivity period it is possible to inform CNS about the duration of cardiac cycle and thus inform it of the heart rate.