Augmentation of Cardiac Contractile Force and Heart Rate by Medulla Oblongata Stimulation in the Cat

Electrical stimulation in two relatively well circumscribed regions of the medulla oblongata elicited tachycardia and augmentation of the right ventricular contractile force recorded by a strain gauge arch technique. One of the two regions was found to be situated within the more central part of the pressor area. Stimulation in this region generally produced vasoconstriction in skeletal muscle parallel with the increased cardiac activity. The second region was found to be located in the“sympathetic vasodilator area” in the ventrolateral part of the medulla. Muscle vasodilatation elicited by stimulation in that region was accompanied by an increase in the cardiac functions. The augmentation of cardiac activity with stimulation of the two regions was mediated by the sympathetic innervation of the heart and, to a minor extent, by an elevated secretion from the adrenal medulla.