Morphine-induced Delayed Cardioprotection And Its Mechanisms In Rabbits

Objectives: (1) To investigate whether morphine could induce the late phase of preconditioning against myocardial ischemia-reperfusion (IR)injury in rabbits . (2) To test if the late phase of preconditioning induced by morphine is mediated by opioid receptor, protein kinase C and K_ATP channel. (3) To investigate the changes of myocardial protein expression profiles 24 h after morphine pretreatment, and to search for the proteins probably involved in the late phase of preconditioning induced by morphine with proteomics techniques.Methods: The experiment consisted of three parts: (1) The late phase of preconditioning induced by morphine. Rabbits were divided into four groups including group Mor-12, group Mor-24,group NS and group IR . A two-day protocol was used.On day 1, morphine (3mg/kg, 30ml) was infused into rabbits in group Mor-12 and group Mor-24 under gerneral anesthesia and controlled ventilation,while the same volume of normal saline(NS) was given to rabbits in group NS.Any treatment was not done in rabbits in group IR in day 1 .Twelve hours after morphine pretreatmen, rabbits in group Mor-12 were subjected to 30 min left anterior descending coronary artery(LAD) occlusions and were reperfused for 2h.Twenty four hours after morphine or NS pretreatmen,rabbits in the other three groups were subjected the same ischemia-reperfusion procedure. Myocardial infarct size and the concentration of cTnI were determined, the incidence of arrhythmia was recorded, the tissue and cell injury of myocardium was examined with optical and electron microscope. (2) Opioid receptor, protein kinase C and K_ATP channel mediate morphine-induced late phase of preconditioning. All rabbits were subjected 30 min myocardial ischemia and 2h reperfusion(IR).Rabbits in group NS and group Mor were given...