Chronic morphine treatment reduces the incidence of ventricular arrhythmias in the isolated rat heart induced by dynorphin1-13 or myocardial ischemia and reperfusion.

We have studied the effects of a daily morphine injection for 2 weeks on induction of naloxone-reversible arrhythmias in the Langendorff isolated rat heart preparation caused by dynorphin1-13 or myocardial ischemia and reperfusion. Chronic morphine treatment significantly reduced the incidence and severity of arrhythmias and increased recovery following both administration of dynorphin and myocardial ischemia and reperfusion. The results support the notion that myocardial ischemia and reperfusion induce cardiac arrhythmias via endogenous opioid peptides.