Quantification of the area under the curve (AUC) after intraperitoneal injection of saline or fentanyl in mice with deletion of µORs in VTA (n = 8 mice) versus control mice (n = 7 mice). Two-way repeated measures ANOVA: group effect, F (1,26) = 4.371, P < 0.05; injection effect, F (1,26) = 23.95, P < 0.0001; group × injection, F (1,26) = 5.777, P < 0.05; Bonferroni post hoc analysis, ** P = 0.0076. Data are mean ± s.e.m.
