Types of the peptide modulation of the vagus nerve effect on the heart rhythm

In anaesthetised cats, effects of 24 regulatory peptides upon inhibitory tonic and synchronizing components of vagal chronotropic action, were studied. The findings allowed to divide the peptidergic vagotropic activity into three types: (1) a selective action upon inhibitory tonic vagal effect; (2) a selective modulation of synchronizing vagal effect; (3) opposite changes in the vagal chronotropic effect components. The peptides seem to be able to modulate both the vagal bradycardia and the functional structure of parasympathetic chronotropic effect.