[Changes of activation sequence in a rabbit sinoatrial node induced by cholinergic influences].

We used high resolution optical mapping for the study of activation sequence in a rabbit sinoatrial node in normal state and during artificial stimulation as well as changes of excitation chronotopography under cholinergic influences. In the norm excitation originates in central region of sinoatrial node. During acetylcholine action (10, 50, 100 M) and activation of intramural parasympathetic nerves suppression of electrical activity in the zone of initial pacemaker localization occurs. Suppression of activation is associated with pacemaker migration within sinoatrial node and lowering of the rate of generation of excitation. Termination of cholinergic influences has been followed by restoration of initial chronotopography of excitation. During artificial stimulation of sinoatrial node nonexitable (refractory) area has been formed in the region of initial localization of the natural pacemaker.