Under conditions of postischemic reperfusion, significance of endogenous opioid receptors' agonists for regulation of the myocardial contractility becomes enhanced. The sigma-receptor blocking contributes to a decrease in postischemic contracture and preservation of the cardiac cell membrane integrity. In sigma-receptor blockade, reoxygenation contracture does not appear. Preliminary mu-receptor blocking leads to an almost complete restitution of the heart contractility and decreases sarcolemma damage during postischemic period.