[Role of enkephalins in the mechanism of anti-arrhythmia effects of adaptation in acute myocardial ischemia].

Adaptation of rats to cold and physical exercise prevented ventricular fibrillation (VF) caused by the occlusion of the left anterior coronary artery. In the heart of adapted rats with acute myocardial ischemia, myocardial enkephalins increased whereas the level of cAMP declined as compared to nonadapted animals. Injection of dalargin before the occlusion of the coronary artery in rats prevented both VF and a decrease of VF threshold. The peptide averted the rise of cAMP content in the heart during acute myocardial ischemia. The data obtained suggest that the rise of endogenous myocardial enkephalins may have an important role in antiarrhythmic action of adaptation. It is assumed that antiarrhythmic effect of enkephalins may be related to the restriction of sympathetic influence on the heart.