Morphine preconditioning, cardioprotection and left ventricular remodelling in rabbits

The objective of this study was to investigate, in a rabbit model, the cardioprotective effect of morphine preconditioning against cardiac remodelling.In male New Zealand rabbits myocardial I/R injury was established by ligating the left descending coronary artery followed by perfusion. The rabbits were randomly divided into: (i) a normal saline sham group (S), (ii) a morphine sham group (MS), (iii) a normal saline group (NS); (iv) a morphine preconditioning group (MPC). After I/R injury, cardiac function was evaluated by echocardiography and biologic markers at day 1, day 3, day 7, day 14, day 21 and day 28. At day 1 after I/R injury, in comparison to the NS group, morphine preconditioning: (i) significantly improved haemodynamic parameters; (ii) reduced myocardial infarct size; (iii) lowered troponin I level. At day 28 after I/R injury, the concentration of B-type natriuretic peptide was significantly lower in the MPC group compared to the NS group. The MPC group had heavier left ventricles than the MS group while the NS group had heavier right ventricles than the other groups, respectively. Furthermore, the MPC group showed improved haemodynamic parameters. Echocardiography showed a higher left ventricular ejection fraction and fractional shorting in the MPC group compared to the NS group at each observation point.After I/R injury and morphine preconditioning by a single dose, we have observed a prolonged cardioprotective effect and an improved cardiac function. Morphine preconditioning may reduce post-infarction remodelling.