( A ) The paw withdrawal latency was obtained by plantar tests before carrageenan injection in the offspring rats (P18) of different groups. (B) The time-course of the hyperalgesia effect induced by carrageenan injection (50 μl, 20 mg/ml). In (B), the different marks and lines represent the results from different groups (filled circle: Control, open circle: M, open square: M + DM, filled square: DM). Data are presented as mean ± SEM. One-way ANOVA followed by the Newman-Keuls test was used to analyze the data. (A: **p < 0.001 for the morphine group vs the control group; B: **p < 0.001, for the morphine group vs the control group) (Control group: n = 8; M group: n = 8; M + DM group: n = 7; DM group: n = 10).