Chronotropic, inotropic, and coronary artery blood flow responses to stimulation of specific canine sympathetic nerves and ganglia.

Electrical stimulation of the major sympathetic cardiac nerves and ganglia in chloralose-anesthetized, open-chest dogs elicited specific changes in heart rate, coronary blood flow, regional intramyocardial pressure, or intraventricular pressure. The effects produced by stimulation of a cardiac nerve were similar to, but never greater than those produced by stimulation of the ipsilateral stellate ganglion. Coronary blood flow was increased when neural stimulation increased intramyocardial pressure. In contrast, coronary blood flow was not altered significantly when neural stimulation induced tachycardia without increasing intramyocardial pressure. It is concluded that in the intact heart, electrical stimulation of the sympathetic cardiac nerves or ganglia increases coronary blood flow by augmenting intramyocardial pressure, not chronotropism.