[Effect of preliminary blockade of alpha- and beta-adrenoreceptors on stress-induced disorders of myocardial relaxation and contractile functions].

Effect of preliminary administration of the alpha-adrenoblocker phentolamine and the beta-adrenoblocker inderal on stress-induced disturbances of myocardial extensibility, contractile function and myocardial resistance to hypoxia and excess Ca2+ was studied on an isometrically contracting isolated right atrium of the rat. Inderal substantially prevented the post-stress decrease in atrial extensibility and almost completely prevented the stress-induced decline in the developed tension and the Frank-Starling mechanism efficiency. At the same time inderal prevented the post-stress increase in hypoxic and hypercalcium contracture of the atrium. Phentolamine did not produce any such protective effects. It is suggested that the damaging action of catecholamine excess occurring under stress is mediated via beta-adrenoreceptors but not via alpha-adrenoreceptors of the heart.