Stereospecific antiarrhythmic effects of naloxone against myocardial ischaemia and reperfusion in the dog

1 The effects of both the (−)- and (+)-stereoisomers of naloxone in anaesthetized dogs with arrhythmias induced by acute coronary artery occlusion followed by reperfusion were investigated. 2 Following coronary artery occlusion and reperfusion, all dogs in the control group developed ischaemia- and reperfusion-induced cardiac arrhythmias, bradycardia and hypotension. 3 The opiate antagonist (−)-naloxone prevented the arrhythmias, bradycardia and hypotension due to myocardial ischaemia and reperfusion. 4 The (+)-stereoisomer of naloxone, which is inactive as an opiate antagonist, was without beneficial effects. 5 These results indicate a possible involvement of endogenous opioid peptides in the cardiac effects due to myocardial ischaemia and reperfusion, mediated by opiate receptors through opiate antagonism.