PROJECT SUMMARY/ABSTRACT - Overall Our Program Project Grant (PPG) focuses on the complex interplay between the chronically infarcted heart and sympathetic nervous system (SNS), with the goal of defining precise mechanisms of ventricular arrhythmias and sudden cardiac death. The overarching objective of the PPG is to test ‘The Spatiotemporal Heterogeneity of Neurotransmitter Release Hypothesis’ that postulates scars alter the ultrastructure of nerves and result in non-uniform neurotransmitter release in the myocardium which is a crucial and proximate cause of lethal arrhythmias. We propose to 1) understand the maladaptive interactions between the chronically injured heart and the SNS, and 2) using this framework to investigate the mechanisms by which chronic vagal nerve stimulation (VNS) as a prototypical neuromodulation therapy exerts its beneficial effects and gain broader insights. Our PPG team has made seminal discoveries in cardiac neural control, cardiomyocyte electrophysiologic function, control of ventricular tachycardia circuits at the myocardial level, and the complex multicellular paradigms that underlie sympathetic neuronal dysfunction within stellate ganglia, the major source of enhanced postganglionic sympathetic drive to the injured heart. These discoveries are relevant to the electrophysiologic instabilities that underlie susceptibility to lethal ventricular arrhythmias and are a result of the multifaceted collaborations between our PPG project & core leaders, and the broader study team. In Project 1, Dr. Shivkumar and his colleagues will utilize novel 3D cardiac electrical mapping approaches combined with real time in vivo neurotransmitter/neuropeptide detection in normal and chronically infarcted beating hearts to define the mechanisms of physiologic and pathophysiologic nerve-myocyte interactions. In Project 2, Dr. Harvey and colleagues will study, at the single myocyte level, how various neurotransmitters (alone and in combinations seen in the normal and diseased myocardial milieu) impact cardiomyocytes from normal hearts and from the scar-border zone. In Project 3, Dr. Ajijola and his colleagues will investigate the source of excessive and dysfunctional sympathetic neurotransmission to the heart, specifically inflammation in the stellate ganglia. Project 3 will investigate how maladaptive interactions between neurons and other cell types such as glia and immune cells lead to dysfunctional control of the chronically injured heart. These three component projects will be supported by two scientific cores, led by Drs. Ardell and Ajijola and an administrative core led by Dr. Shivkumar. The scientific cores will provide a stream of normal and diseased human hearts and stellate ganglia for studies in Projects 1-3, as well as high throughput tissue clearing techniques and high-resolution imaging (Core A). The cores also aim to reproducibly generate experimental porcine models and oversee technologies for in vivo neuropeptide/neurotra...