Figure 2. Morphine antagonizes DOX-mediated enhancement of intercellular O₂^•− and H₂O₂ levels in SH-SY5Y cells.

(A) Cells were treated with 4 μM DOX for the indicated time periods, and the intracellular O₂^•− and H₂O₂ levels were detected by flow cytometry using 5 μM HE and 10 μM DCFH₂-DA as fluorescent probes as described in the Materials and methods section. The Figure is representative of four independent experiments yielding similar results. (B and C) Cells were treated with either 4 μM DOX alone or with 4 μM DOX in combination with 200 μM morphine (Mor) for 24 h, and then the intracellular O₂^•− and H₂O₂ levels were detected. (B) Representative image of five independent experiments yielding similar results. (C) Quantification of O₂^•− and H₂O₂ generation. Values are means±S.E.M. for at least three independent experiments performed in triplicate (^##P<0.01 compared with control; *P<0.05 and **P<0.01 compared with DOX alone).