Circulatory Responses to Electrical and Reflex Activation of the Nervous System after Cardiac Denervation

Rigorous testing procedures assessed the extent of extrinsic cardiac denervation in three groups of animals subjected to cardiac extirpation and reimplantation (E&R), mediastinal neural ablation (MNA) or thoracic ganglionectomy (BSTG). After E&R, all dogs were completely denervated. Evidence for vagal reinnervation appeared as early as 26 days and for both vagal and sympathetic reinnervation in 74 days. After one, two and three years, the functional responses to reflex and electrical activation of the nervous system were similar to those in normal dogs. After MNA, only one animal of eight was totally denervated. Seven showed varying degrees of cardiac activation in response to diencephalic stimulation or stimulation of the cardiac sympathetic nerves. Thus MNA, though surgically feasible, cannot be assumed to be successful without rigorous testing. After BSTG, four of eight dogs showed complete separation of sympathetic cardiac outflow from the CNS; in all eight, moderate to large cardio-accelerator responses were elicited from the distal vagosympathetic trunk after atropinization. There is little correlation between the over-all cardiac responses persisting in all operated animals and total cardiac catecholamine content, or between cardio-accelerator responses and right atrial catecholamine content.