[The components of the negative chronotropic effect of the vagus nerve on the heart and a method for their definition].

Abstract

Stimulation of the peripheral end of the right n.vagus led to synchronizing of the vagal and cardiac rhythms in anesthetised cats. The stimulation of the n.vagus beyond the synchronizing range resulted in the sinus arrhythmia. The negative chronotropic effect of the vagus nerve on the heart was shown to consist of tonic as well as synchronizing components. The latter component did not depend on the heart rate and may be expressed as a difference between the maximal and minimal cardiac cycle during the sinus arrhythmia. The tonic component was determined as a difference between the initial cardiac cycle and the minimal cardiac cycle during the sinus arrhythmia. It seems to be cumulative in nature and to depend on the heart rate.