Depression of Ventricular Contractility by Stimulation of the Vagus Nerves.

• Numerous workers have investigated the effects of stimulating the vagus nerves upon ventricular contractility in the mammalian heart. Many of these investigators" concluded that vagal stimulation has little or no influence on the contractility of the ventricles, while others^ deduced that it elicits a negative inotropic effect. Currently, the former opinion appears to be almost universally accepted. However, certain experimental observations encouraged us to reinvestigate this problem. It was found that electrical stimulation of the distal ends of the cervical vagi provokes a more marked increase of coronary flow during systole than during diastole in the paced, canine heart which is perfused at constant pressure. In other experiments, it was observed that the negative inotropic effect upon the canine ventricles which is elicited by stimulation of the carotid body chemoreceptors is abolished by bilateral cervical vagotomy." These observations suggest that the vagus nerves may play a definite role in the nervous regulation of the contractility of the ventricular myocardium in the mammalian heart. The experiments described in this paper confirm this hypothesis. A preliminary report of some of these experi-