Negative Inotropic Effect of the Vagus Nerves upon the Canine Ventricle

In an innervated, paced, left heart preparation in which the left ventricle contracted against a constant volume of incompressible fluid (isovolumetric preparation), electrical stimulation of the distal end of either sectioned cervical vagus nerve decreased the peak tension generated by the teft ventricle. The vagi, therefore, exert a negative inotropic effect directly upon the ventricular myocardium.