[Effect of adaptation to physical loading on the adrenoreactivity of the isolated rat atrium]

The experiments on the isolated atria of rats, previously adapted to swimming exercises, have established a significant decrease in the heart rate and an increase in positive inotropic effect of noradrenaline (4 X 10(-7) and 6 X 10(-7) M). After beta-adrenoceptor blockade with propranolol (2 X 10(-6) M) the inotropic effect of an alpha-adrenoceptor agonist mezaton on the isolated atrium of the adapted rats was greater than in nonadapted controls.