[The chronotropic effect of maximal stress on the heart and its regulation]. 
The reflex bradycardia occurring at the maximal isometric heart strain produced by clamping of aorta was shown to be less intense if the heart rate prior to the experiment had been low.  Vagotomy prevented or decreased the bradycardia.  The beta-adrenoreceptor blockade with inderal significantly reduced the bradycardia, whereas the alpha-adrenoreceptor blockade with tropaphen increased it.  The important role of relationship between adrenergic and cholinergic regulation of the heart in development of the bradycardia was discussed.