Activation of cardiac sympathetic afferents during coronary occlusion. Evidence for reflex activation of sympathetic nervous system during transmural myocardial ischemia in the dog.

Left ventricular sympathetic afferent nerves are located mainly in superficial epicardial layers. Reflex excitatory responses mediated by sympathetic afferent nerves have been observed during myocardial ischemia in cats and humans but not in dogs. Previous canine studies have induced ischemia by occlusion of a coronary artery. Extensive collateral circulation in the canine heart may limit ischemia of epicardial layers during simple coronary occlusion, resulting in little stimulation of sympathetic afferent nerves and minimal reflex excitatory responses.