Localization of neurally mediated arrhythmogenic and coronary vasoconstrictor properties of digitalis.

Studies of the cardiotoxicity of digitalis have revealed an appreciable role of the autonomic nervous system in modulating these toxicities. Neuraxis transection experiments and studies with digitalis compounds that fail to enter the central nervous system suggest that centers localized to the floor of the fourth cerebral ventricle play a substantial part in neural arrhythmogenic effects of the digitalis glycosides. Stimulation of the area postrema (AP) in animals partially digitalized, but not otherwise manifesting ventricular arrhythmias, elicits ventricular tachycardia. Neuraxis transection experiments and studies with a charged digitalis derivative also suggest localization of the coronary vasoconstrictive properties of digitalis to the AP. The results suggest that this region of the brain stem is sensitive to neurally active substances that cause peripheral sympathetic effects of considerable consequence.