[Changes in the bioelectrical activity of pacemaker cells of the desympathized and reserpinized frog heart under conditions of parasympathetic rhythm acceleration].

A study was made of the mechanism of parasympathetic acceleration on Rana temporaria hearts with the preliminarily exhausted catecholamine stores due to desympathization and reserpinization of the animals. Bioelectrical activity of the cells of the isolated pace-maker was recorded. Parasympathetic acceleration was accompanied by an increase in the rate of accretion of slow diastolic depolarization (this indicating an active mechanism of this acceleration), and also a slight hyperpolarization and a decrease of the action potential duration. The acceleration effect and the changes of the form of the action potential were absent after atropine treatment of the preparation, this confirming the cholinergic nature of the parasympathetic acceleration. It is supposed that the parasympathetic system mediator acetylcholine--could decrease potassium or increase sodium permeability of the Pacemaker cell membrane, this leading to increase of the slow diastolic depolarization rate and to discharge acceleration.