[Influence of atropine on the chronotropic effects of stimulating the parasympathetic innervation of the heart].

Changes of the positive chronotropic effect in the frog atrium during stimulation of the extracardiac pathways or of the central end of intracardiac innervation after application of atropin (10(-4)--10(-5) on the sinus node, were studied. The positive chronotropic effects were abolished by the atropin application. The postganglionic impulse activity of the intracardiac nervous pathways did not change. Atropin had no influence on the sympathetic acceleration of the heart rate due to stimulation of sympathetic pathways. Positive chronotropic effects induced by stimulation of the parasympathetic extra or intracardiac pathways, are of cholinergic nature.