Factors affecting the protective effect of morphine preconditioning on murine hippocampal neurons against anoxia-reoxygenation injury / 中华麻醉学杂志

ABSTRACT

Objective To investigate the factors affecting the protective effects of morphine preconditioning on murine hippocampal neurons against anoxia/reoxygenation (A/R) injury and the underlying mechanisms.Methods Hippocampal slices (400 μm thick) were prepared using hippocampi isolated from decapitated mice. A/R injury was simulated in vitro using artificial cerebral spinal fluid (ACSF) deprived of O_2 and glucose for 20 min followed by reoxygenation and glucose supply for 2 h. The experiment was performed in 4 parts I .The slices were incubated with 5 different concentrations of morphine (0.1, 0.3, 0.5, 1.0, 3.0, 10.0 /μmol/L) for 30 min at 30 min before A/R; Ⅱ. The slices were incubated with morphine 3.0 /μmol/L for 5 different periods of time (5, 15, 30, 45, 60 min) at 30 min before A/R; Ⅲ. The slices were incubated with morphine 3.0 μmol/L for 30 min followed by A/R at 6 different intervals (0, 5, 15,30,60, 120 min); Ⅳ. The slices were incubated with (a) chelerythrine (a non-selective PKC antagonist) 10 /μmol/L or (b) εVl-2 (a selective nPKCe isoform antagonist) 2 μmol/L or (c) AIP 2 μmol/L (a selective CaMK Ⅱ antagonist) or (d) MK-801 10 μmol/L (a non-competitive NMDA receptor blocker) for 30 min and then for another 30 min together with morphine 3.0 μmol/L before A/R at 30 min interval. The survival rates of the hippocampal neurons were assessed by TTC staining. Results Neuronal survival rates were significantly higher in morphine preconditioning groups which preconditioned with morphine (0.5-10.0 μmol/L) for 15-60 min at an interval of 0-60 min before A/R than in A/R group. Increase in neuronal survival rate induced by morphine preconditioning was partially blocked by chelerythrine or εV1-2 or AIP or MK-801. Conclusion Preconditioning with appropriate concentrations of morphine (0.5-10.0 μmol/L) for appropriate period of time (15-60 min) at appropriate interval (within 60 min) before A/R can protect hippocampal neurons against A/R injury through activation of nPKCε, NMDA receptor and CaMKⅡ.