Figure 1. Morphine modulates lineage-specific differentiation of neural progenitor cells.

(A) Adult hippocampus-derived neural progenitor cells were cultured in complete differentiation medium for 4 d, with or without the treatment of 1 μM morphine or 10 nM fentanyl, and 10 μM CTOP. Cells were stained with markers for neurons (Tuj1), astrocytes (GFAP), oligodendrocytes (O4) and with DAPI. Scale bar, 25 μm. Images are representative of at least three independent experiments with similar results.

(B) Quantification of cells stained with each marker, calculated as the percentage of the total number of cells stained with DAPI. Red: Tuj1; Green: GFAP; Purple: O4. *, p<0.05 between indicated groups. #, p<0.05 compared to Tuj1 in control group. Data are the mean ± SEM of at least three independent experiments.

(C) The expression of βIII-tubulin, GFAP and MBP were determined by real-time PCR after 4 d of differentiation. The results were normalized against those of GAPDH, and further normalized against the result obtained from untreated cultures in the control group. All data represent the mean ± SEM of four independent experiments. *, p<0.05; **, p<0.01 between indicated groups.

(D) CD-1 mice (8-week-old males) received daily i.p. injections of 300 mg/kg BrdU for 3 consecutive days, followed by CPP training with subcutaneous injection of 5 mg/kg morphine or an equal volume of saline. Brains were fixed at day 14 and then sectioned for BrdU staining and co-immunostaining with Tuj1 and GFAP antibodies, and DAPI. Cells co-stained with antibodies of both BrdU and Tuj1 or GFAP are indicated by white arrows. Scale bars, 50 μm.

(E) Total numbers of BrdU-labeled cells co-stained with Tuj1 or GFAP antibodies in mouse hippocampus sections were counted and compared. Data represent the mean ± SEM of six independent experiments. *, p<0.05 compared to the number of cells with the same positive marker in the saline group.