['Sufentanil is widely used in clinical anaesthesia because of its protective effects against ischaemia/reperfusion injury. Diabetes mellitus elevates the activity of glycogen synthase kinase-3β (GSK-3β), thereby increasing the permeability of mitochondrial transition pore. This study investigated the role of GSK-3β in ameliorating the cardioprotective effect of sufentanil post-conditioning in diabetic rats.', 'Streptozotocin-induced diabetic rats and age-matched non-diabetic rats were subjected to 30 min of ischaemia and 120 min of reperfusion. Five minutes before reperfusion, rats were administered one of the following: a vehicle, sufentanil (1 μg/kg), or a GSK-3β inhibitor SB216763 (0.6 mg/kg). Myocardial infarct size, cardiac troponin I, and the activity of GSK-3β were then assessed.', 'Sufentanil post-conditioning significantly reduced myocardial infarct size in the non-diabetic, but not in diabetic rats. SB216763 reduced infarct size in both diabetic and non-diabetic animals. Sufentanil-induced phospho-GSK-3β was reduced 5 min after reperfusion in diabetic rats, but not in non-diabetic rats.'] Does diabetes mellitus abrogate the cardioprotection of sufentanil against ischaemia/reperfusion injury by altering glycogen synthase kinase-3β?