Responses of Individual Cardiac Chambers to Stimulation of the Cervical Vagosympathetic Trunk in Atropinized Dogs

Employing multiple chamber pressure recording techniques, the presence of fibers within the right and left cervical vagosympathetic trunks which innervate both right and left ventricles has been demonstrated. Electrical excitation of the cervical vagosympathetic in the atropinized dog elicited a distinct increase in both rate of rise and in maximal systolic intraventricular pressures, with or without cardiac acceleration. It persisted during electrical pacing of the right ventricle. In many animals, the a-wave of the atrial pressure traces also showed augmentation, but this was not consistent or essential for the ventricular response. Although pulmonary vasoconstriction was not ruled out as a concurrent event, its contribution to right ventricular augmentation was not essential as demonstrated in bilateral, isovolumetric ventricular preparations. The evidence indicates the presence of adrenergic fibers in the cervical vagosympathetic trunk which are distributed to all four cardiac chambers. Their effects on the heart are abolished by the β-blocking agent, propranolol, and are unaffected by eserine administration.