Postnatal methadone-induced rewarding effects on prenatal methadone or DM exposed offspring. Rewarding effects induced by methadone (MD, 6 conditioning at 4 mg/kg, s.c.) in male adult offspring. Data are presented as mean ± S.E.M. (n ≥ 8). *P < 0.05 and ***p < 0.001 when compared to pre-conditioning data of its own group; ###p < 0.001 when compared to post-conditioning data of the control group.