Neural control of the heart during arrhythmias and exercise.

Involvement of neural activity during cardiovascular adjustments and during arrhythmias can be determined by comparing the results of cardiovascular changes after lesions are made in nuclei or pathways of the central nervous system or ablations of ganglia or nerves are made in the peripheral nervous system. The neural effects can be exaggerated if these systems are forced to perform at higher levels during a stressful situation. The purpose of this presentation is to discuss the responsiveness of the cardiovascular system after left or right stellate ganglionectomy and after lesions are made in the fastigial nucleus of the cerebellum in dogs stressed with submaximal exercise. These dogs are implanted with instruments that are designed to measure cardiovascular responses. Hypotheses for potential neural mechanisms are generated from the results of chronic animal studies, and these mechanisms are tested in anesthetized dogs and cats. Electrical stimulation of ascending and descending pathways in the central nervous system and stimulations such as coronary occlusion and mechanical probing are used to activate neural mechanisms in the anesthetized state. A general schema concerning the results of our studies provides further information about our approach to understanding the physiological role that the central nervous system may exert on the cardiovascular system during stress.