ON THE MECHANISM OF THE CARDIOVASCULAR ACTIONS OF DIGITALIS; OBSERVATIONS ON THE INFLUENCE OF FLAXEDIL, ATROPINE OR VAGOTOMY

¹ Department of Pharmacology, McGill University, Montreal, Canada

The effects of Flaxedil, atropine and vagotomy upon the cardiovascular respouses to ouabain and digitoxin have been studied in morphinized dogs anesthetized with pentobarbital sodium under artifleal respiration. (a) It is confirmed that Flaxedil exerts an atropine-like action in the heart, blocking both cardioinhibitory vagal reflex effects and acetylcholine action, while the depressor respouse to acetylcholine is potentiated. The effects of vagotomy and atropine on these responses have also been studied. (b) It is shown that after injection of either Flaxedil or atropine, both ouabain and digitoxin induce a strong afferent vagal vasomotor inhibitory effect arising from the heart. While the exact origin or pathway of this reflex has not been determined, it is suggested that it might be the same as the so called "Bezold Reflex" or "Bezold Effect". (c) The above findings might explain certain phases of the older controversial digitalis literature, and it is suggested that this action might be an important factor in the therapeutic value of digitalis in cardiac failure. The problem is being further studied.

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