Immunoblot results for ΔFosB expression in the caudate-putamen and nucleus accumbens following repeated vehicle or THC administration in wild type and CB1R knockout mice. Blots were probed with antibodies directed against ΔFosB and α-tubulin (loading control). (A and B) Graphs showing densitometric analysis of brain regions from vehicle- and THC-treated mice expressed as percent vehicle control. For CPU, data are means ± SEM with ^ p < 0.05 and ^^ p < 0.01 versus wild type vehicle controls, Dunnett’s post-hoc test following a one-way ANOVA, n = 7–8 mice per group. For NAC, data are means ± SEM with * p < 0.05 versus wild type vehicle controls, Bonferroni post-hoc test following a two-way ANOVA, n = 7–8 mice per group. (C and D) Representative blots showing ΔFosB-ir and α-tubulin-ir in vehicle- and THC-treated brains of wild type and CB1R knockout mice for each region examined.