Cardiac vagal chemosensory afferents. Function in pathophysiological states.

Stimulation of cardiac vagal afferent endings evokes reflex hypotension and bradycardia, also known as a Bezold-Jarisch effect. The physiological importance of this reflex pathway remains uncertain today, but it is increasingly apparent that cardiac vagal afferents can play an important role in modulating cardiovascular control in pathophysiological states, particularly myocardial ischemia. The afferent endings that compose this vagal input are functionally diverse. Ventricular endings exist that are stimulated by wall motion. However, cardiac chemosensitive endings, stimulated by a variety of metabolically active substances known to be produced by the stressed myocardium (e.g., bradykinin, prostaglandins, reactive oxygen species), play a major role in mediating reflex adjustments during myocardial ischemia. Data are presented highlighting the importance of arachidonic acid metabolites and oxygen radicals in activating cardiac vagal endings during myocardial ischemia and reperfusion, and their role in modulating cardiac afferent sensitivity in the disease states of heart failure and insulin-dependent diabetes.