Left ventricular receptors: physiological controllers or pathological curiosities?

Mechanically and chemically sensitive receptors in the ventricle have been described histologically and electrophysiologically. Early experiments documented the hypotension and bradycardia that resulted from the intracoronary administration of one of the veratrum alkaloids (the Bezold-Jarisch reflex). Mechanical distension of the ventricles also results in a reflex decrease in heart rate and a reduction in peripheral resistance. Skeletal muscle and coronary vascular resistance appear to be most prominently affected by stimulation of ventricular receptors. Coronary ischemia has also been shown to evoke reflex effects which are attributable to stimulation of ventricular receptors. The resultant bradycardia can be especially ominous in acute myocardial infarction. Changes in myocardial inotropic state have been shown to alter ventricular receptor discharge in experimental animals. This stimulus may evoke reflex changes in peripheral hemodynamics. A variety of humoral substances can alter ventricular receptor discharge and evoke Bezold-Jarisch like responses. These include bradykinin and prostaglandins. PGI2, when given intracoronary in small doses or intravenously in larger doses will lower blood pressure while inhibiting the baroreflex induced tachycardia. It has also been shown in some experiments that PGI2 and arachidonic acid can evoke overt bradycardia and hypotension via a reflex mechanism. The role of prostaglandins in cardiovascular reflex control may be important in pathophysiologic states such as coronary ischemia and heart failure. Ventricular receptors can interact centrally with the arterial baroreceptors to attenuate the baroreflex control of both heart rate and peripheral resistance. Finally, the stimulation of ventricular receptors can alter a variety of humoral substances which are important regulators of cardiovascular and fluid volume homeostasis. These include vasopressin, renin and catecholamines. Those studies which have been done within the last 10 years or so, especially in unanesthetized animals, have demonstrated that the Bezold-Jarisch reflex is more important to cardiovascular control than previously thought. Future work will be necessary to determine the precise role ventricular receptors play in various pathological situations.