The role of opioid receptor agonists in ischemic preconditioning

Opioids and their receptor agonists have been widely used because of their beneficial effects on pain management and control. Over the past decade, there has been an increasing interest on the experimental use of opioid agonists in the laboratory setting of ischemia and reperfusion; existing data suggest that there is a potential association between opioid agonism and the reduction of infarct size in several animal models of regional ischemia similar to that following ischemic preconditioning. Most of these studies seem to attribute these beneficial and cardioprotective effects to the stimulation of a specific opioid receptor type, the delta (δ) opioid receptor. This review focuses on the role of the delta opioid receptor agonism in several models of ischemia and reperfusion, as well as on hemorrhagic shock models, on the potential mechanisms of action following delta opioid receptor activation and on the time window for opioid administration in various animal studies.