The most powerful protective mechanism against ischemia-reperfusion injury other than rapid reperfusion is ischemic preconditioning. Ischemic preconditioning is defined as the development of tolerance to ischemia-reperfusion injury by a previous short bout of ischemia resulting in a marked reduction in infarct size. This mechanism can be mimicked by several pharmacological substances such as adenosine and morphine.

We, the researchers at Radboud University Nijmegen Medical Centre, have recently developed a method in which we can detect ischemia-reperfusion injury in the human forearm by using Annexin A5 scintigraphy (Rongen et al). With this method we will determine whether opioid receptors are involved in ischemic preconditioning. We expect to find that morphine can mimic ischemic preconditioning and that acute ischemic preconditioning can be blocked with the opioid receptor antagonist naloxon. This study will increase our knowledge about the mechanism of ischemic preconditioning and may also provide leads to exploit this endogenous protective mechanism in a clinical setting.