Responses of atrial and aortic baroreceptors to nonhypotensive hemorrhage and to tranfusion

Abstract

The activity of aortic and atrial type B baroreceptors was compared in 21 experiments in 15 chloralose-in-saline anesthetized dogs in the course of stepwise bleeding and transfusion. When the alteration-in-pulse frequency was taken into account, the integrated impulse rate or "drive" from the aortic receptors was found to remain essentially constant during moderate volume changes. However, there was a sharp alteration in the activity of the atrial receptors. This amounted to an 80% decrease in firing rate with a 20% blood volume loss and a fourfold increment with a 20% increase in blood volume. The triggering during nonhypotensive hemorrhage of various homeostatic responses such as tachycardia and the release of anti-diuretic hormone is discussed in relation to the above disparity of receptor drives.