[Effect of a single stimulation of the vagus nerve on heart rate in cats]

The single stimulation of the vagus nerve evokes two waves of chronotropic effect. The first wave is characterized by large amplitude and short duration comparable in time with one cardiac cycle. The second wave begins somewhat later, has low amplitude and lasts during 20--25 cardiac cycles. The role of the first wave in synchronization of cardiac pacemaker with vagal stimulation is discussed. The second wave seems to reflect tonic influences of the vagus nerve on the heart rate.