Inhibition of carotid pressor response by left aortic depressor nerve in dogs.

In 12 conscious dogs, the mean increase of 26 mmHg in arterial pressure during carotid occlusion was augmented by 52 mmHg after section of the left cervical vagus nerve and 6 mmHg after right vagal section. In 18 anesthetized dogs, in which the cervical vagal nerves were reversibly cold blocked, corresponding values were 33, 28, and 6 mmHg, respectively. In nine of these dogs, this left-sided dominance was present after bilateral section of the vagal cardiopulmonary afferents; it was absent after bilateral section of the aortic nerves in the other nine dogs. In five dogs on cardiopulmonary bypass with heart and lungs excluded, pressure within the isolated aorta and major intrathoracic arteries was raised from 120 to 220 mmHg. The resultant hypotension reflexly induced by activation of aortic baroreceptors was reduced by left but not by right vagal cold block. It was concluded that, in the dog, the left aortic nerve provided the major inhibition of the increase in arterial pressure after carotid occlusion.