Cardiac responses to stimulation of thoracic afferents in the primate and canine.

Excitatory cardiovascular responses to electrically stimulated upper thoracic sympathetic afferent nerves were observed in halothane-anesthetized mongrel dogs and monkeys. The central end of the transected ventral limb of the left ansa subclavia was stimulated before and after several types of denervation. Significant increases in right and left ventricular maximum systolic pressures, systolic and diastolic systemic blood pressures, and aortic flow were observed. The carotid sinuses were denervated bilaterally and stimulation of the ansa was repeated. The cardiovascular responses to stimulation of the ventral ansa after carotid sinus denervation were greater in magnitude than those observed prior to denervation. This carotid sinus modulation of cardiovascular responses was observed in dogs and monkeys. Cardiovascular responses to stimulation of the ventral ansa after bilateral vagotomy were significantly less than the responses observed after carotid sinus denervation prior to vagotomy. However, the responses after vagotomy were statistically identical to responses obtained while stimulating the ventral ansa when the carotid sinuses and vagi remained intact.