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

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Abstract
The reflex effects of an acute reduction of atrial receptor activity was studied in conscious dogs. Dogs were prepared surgically with a pericardial pouch that enclosed 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. Some ventricular receptors probably 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. Atrial receptors are capable of reflexly influencing salt and water excretion and plasma renin activity. The potential physiological significance of these reflexes during normal day-to-day activities needs to be determined.