Protective effect of the vagotonic action of morphine sulphate on ventricular vulnerability

Administration of morphine sulphate to 16 anaesthetised dogs resulted in significant reduction in ventricular vulnerability to fibrillation. The repetitive extrasystole threshold was used as an index of vulnerability to ventricular fibrillation. In 14 dogs, atropine or vagotomy abolished this response. This suggests that central vagal activation by morphine sulphate may be protective against ventricular fibrillation.