Adolescent exposure to oxycodone modulates dopamine-related gene expression in adulthood. The average (mean ± SEM) relative expression of (a) D1 receptor in the NAc, (b) D2 receptor in the NAc, (c) MOR in the NAc, (d) DAT in the VTA, (e) TH in the VTA, and (f) MOR in the VTA for adult mice that were exposed to sham surgery (striped bars; n = 6 - 8) and oxycodone (solid bars; n = 6 -7) during adolescence. Asterisk indicates a significant difference between drug exposure groups (*, p < 0.05)