The effect of adaptation to stress exposures and to periodic hypoxia on the cardiomyocyte trigger activity of the papillary muscles in the rat]

Action potential of cardiomyocytes was recorded in experiments on isolated papillary muscle of the rat left ventricle. The effect was estimated of preliminary adaptation to intermittent hypobaric hypoxia or to short-term stress exposure on the incidence and the pronouncement of delayed after depolarization and of trigger activity induced by a high frequency stimulation against the background of isoproterenol (10(-8) M). It was shown that adaptation to hypoxia or to stress reduced the incidence of delayed after depolarization and of trigger activity, adaptation to stress exerting a more pronounced effect. Immobilization stress (6 hours) potentiated the trigger activity, adaptation to stress exerting a more pronounced effect. Immobilization stress (6 hours) potentiated the trigger activity and this potentiation was effectively prevented by either type of adaptation.