Thoracic Chemoreceptors in the Dog

Anatomical and electrophysiological techniques were employed to investigate the aortic bodies in anesthetized puppies and dogs. The microscopic appearance, location, innervation, and vasculature of the aortic bodies were investigated by microdissection and histological examination of gelatineinjected preparations. Thoracic chemoreceptor impulses were recorded from the cervical vagus nerves, the nervous pathways in the thorax identified by cold blockade, and the blood supply to the receptors investigated by injection of drugs. Large, circumscribed aortic bodies were few, the majority of glomus cells being scattered in small groups along the vagal branches coursing on the walls of the pulmonary artery and aorta. Very few bodies were found in groups 1 and 2 at the right and left subclavian angles. The majority were in group 3, ventral to the aortic arch and pulmonary bifurcation and supplied by the ventromedial cervical cardiac branch of the left vagus, and in group 4, between the aorta and pulmonary artery, supplied by the recurrent cardiac branch of the right vagus. The arterial supply to the aortic chemoreceptors stemmed from the aorta and the brachiocephalic and left coronary arteries. In neither puppies nor adult dogs was there evidence of a supply from the pulmonary artery. ADDITIONAL