Electrophysiological Properties of Intrinsic Cardiac Neurons

Abstract

Abstract Cardiac performance is determined by the rate and strength of contraction of the heart. There is increasing evidence indicating that intrinsic cardiac neurons interact with extracardiac intrathoracic ganglia and the central nervous system to control the heart and are capable of independently monitoring and influencing cardiac function. Aspects of cardiac function that are subject to control by intracardiac neurons include chronotropic actions (changes in heart rate), dromotropic actions (changes in conduction of excitation) mediated by pacemaker and conducting cells, and inotropic actions (changes in contractile force) mediated by atrial and ventricular myocytes. In addition, the coronary circulation and aspects of cardiac valve function are likely to be influenced. Evidence obtained from histochemical, electrophysiological, and pharmacological studies both in vivo and in vitro strongly suggest that neurons form functional afferent, efferent, and local circuits within the cardiac nerve plexus. This plexus acts as a complex site for the integration and modification of sensory in­ put and cardiac output. Indeed, rather than being a simple relay station, the cardiac nerve plexus seems to share many similarities with the complex neural network of the enteric nervous system.