Obligatory Role of Cardiac Nerves and α1-Adrenergic Receptors for the Second Window of Ischemic Preconditioning in Conscious Pigs

We tested the hypothesis that cardiac nerves may mediate ischemic preconditioning. Pigs were chronically instrumented to measure aortic, left atrial and left ventricular pressures, and regional myocardial function (wall thickening). Hemodynamic variables, area at risk, and tissue blood flows (radioactive microspheres) were similar among groups. Myocardial infarct size following 60 minutes coronary artery occlusion and 4 days reperfusion, expressed as a fraction of the area at risk, was 42±4.0%, in innervated pigs and similar in pigs with regional cardiac denervation (CD, 41±2.5%). Infarct size in innervated pigs during the first window of preconditioning (first window) was markedly reduced (6±1.8%, P