THE EFFECT OF ACETYLCHOLINE ON ADRENALINE-INDUCED SUBATRIAL RHYTHMS IN THE SENSITIZED CAT HEART

Acetylcholine has been shown to be an effective antiarrhythmic agent against arrhythmias induced by adrenaline in combination with the myocardial sensitizers petroleum ether, halothane, and harman methosulphate. It has also been shown that acetylcholine will reduce or prevent the increase in ventricular automaticity produced by adrenaline in the intact cat and in the isolated papillary muscle of the cat. All of these actions of acetylcholine can be blocked by atropine. Evidence from experiments in which petroleum ether inhalation was begun after an arrhythmia had been induced by adrenaline indicated that petroleum ether was causing an increase in ventricular automaticity. The results appear to support the idea that petroleum ether and possibly other sensitizers interfere with the stabilizing action of endogenous acetylcholine on the ventricle and allow the stimulating action of adrenaline to produce severe prefibrillatory rhythms by an increase in ventricular automaticity.