STUDIES ON VERATRUM ALKALOIDS. XXX. THE ACTION OF SOME ESTERS OF GERMINE ON CARDIAC OUTPUT AND VASCULAR TONE WITH OBSERVATIONS ON DRUG-INDUCED DECREASE OF POSITIVE INOTROPIC SYMPATHETIC TONE

¹ Department of Pharmacology, Harvard Medical School, Boston, Massachusetts
² Department of Pharmacology, The University of Buffalo, School of Medicine, Buffalo, New York
³ Depart ment of Pharmacology, Women's Medical College, Philadelphia, Pennsylvania

The nature of the hypotension produced by several esters of germine and by veratridine has been investigated in the open-chest preparation of the dog. Cardiac output and vascular tone both decrease after intravenous injection of effective doses of all alkaloids and both changes participate in the fall in blood pressure. The relative contribution of each of these factors depends upon the level of cardiac output and vascular tone existing before the injection.

During the period of drug-induced decrease of cardiac output the atrial pressures were either slightly decreased, not changed, or increased. In 19 out of 31 reactions the filling pressures were increased. In these cases the fall in output was probably due to a decrease in myocardial contractility. A neurogenic influence upon myocardial contractility has been reported recently by several investigators. A decrease of myocardial contractility, attributable to nervous influences, during the action of drugs which are known to cause a decrease in sympathetic vasoconstrictor tone implies the existence of a neurogenic positive inotropic tone.