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Dexamethasone antagonizes morphine effects on GSSG levels

Dexamethasone (DEX) is a highly potent logacting glucocorticoid with negligible sodium retaining properties. Recent evidence has been obtained for an interference caused by DEX on morphine induced analgesia, hypermotility, constipation and contraction of guinea pig isolated ileum. Studies in our laboratory have recently focused on the relationship between morphine and glutathione (GSH) levels. The present study was carried out to determine whether DEX may affect the morphine induced GSH variation in the brain. Male albino Wistar rats (180-200 g) received i.p. morphine (100 mg/kg), DEX (10 mg/kg) and were sacrificed 3 hours after the administration, in the brain GSH and glutathione disulfide (GSSG) were determined by an automatic procedure developed in our laboratory. The results show that DEX is not able to inhibit the GSH levels induced by morphine but completely counteracts the effect on GSSG levels (nmoles/g tissue). In fact, the GSSG for the control group was found to be 2.8+0.56 for the morphine treated group was 5.7+0.46 for the DEX treated group was 3.0+0.49 and for the DEX+Morphine treated group was 3.0+0.48. The present study shows that DEX is also able to interfere with morphine induced GSH variation

Author(s): Federica Cavallo, Lucia Micheli, Giorgio Giorgi and Anna Capasso