Reflex effects of cephalic hypoxia, hypercapnia, and ischemia upon ventricular contractility.

• In the vagotomized dog with deafferented peripheral chemoreceptors, hypoxia, hypercapnia, or ischemia of the central nervous system provokes reflex, positive chronotropic and inotropic effects upon the normally oxygenated heart. Bradycardia and depression of myocardial contractility are considered to be the primary reflex effects upon the canine heart elicited by stimulation of the chemoreceptors of the carotid bodies." Adequate information is not available concerning the effects of hypoxia, hypercapnia, or ischemia of the central nervous system and the carotid bodies conjointly upon the normally oxygenated ventricles. In the present study, this problem has been investigated in an innervated, isovolumetric, left ventricle preparation.