Cardiovascular,Renal,and Humoral Effects of Applying Local Anesthetic to the Atria of Conscious Dogs 1

Abstract

Abstract

We studied the reflex effects of an acute reduction of atrial receptor activity in conscious dogs. In order to accomplish this, dogs were prepared surgically with a pericardial pouch that enclosed either both atria or a single atrium. The experiments were performed after the animals had recovered from the operation. Atrial receptor activity was decreased by perfusing a local anesthetic, lidocaine, through the pericardial pouch. The effectiveness of this technique was documented in anesthetized dogs by recording atrial type B receptor activity from the cervical vagus. It is likely that some ventricular receptors also were blocked with this technique. In the conscious dog, perfusion of each type of pouch with lidocaine consistently produced decreases in urine flow and salt excretion, but these changes were usually modest and did not consistently achieve statistical significance. Hemodynamics were relatively little affected in these experiments, but aortic pressure and left atrial pressure did rise significantly when lidocaine was added to the pouch that enclosed both atria. Plasma renin activity increased significantly during lidocaine perfusion in each series of experiments. These data are consistent with the concept that atrial receptors are capable of reflexly influencing salt and water excretion and plasma renin activity. Further work is needed to determine the potential physiological significance of these reflexes during normal day-to-day activities.