A. Dose dependent effect of KOR-agonists U69,593 and U50,488 on SERT activity: Synaptosomes prepared from ventral and dorsal striatum were preincubated with Vehicle-E or various concentrations of U69,593 (μM: 2.5, 5, 10) or Vehicle-B or U50,488 (μM: 2.5, 5, 10) for 15 min at 37°C before 5-HT uptake assays. Treatment with BNI (1 μM, 60 min) was carried out prior to U69,593 or U50,488 (10 μM, 15 min) treatment. 5-HT uptake was determined after 6-min incubation at 37°C using [3H]labeled 5-HT (40 nM) as described under “Materials and Methods”. SERT specific 5-HT uptake was determined by subtracting 5-HT accumulation in the presence of 0.1 μM fluoxetine from total 5-HT accumulation (in the absence of fluoxetine). The results were presented as percent change from corresponding vehicle treated controls. Both U69,593 and U50,488 decreased SERT activity (One-way ANOVA: U69,595/ventral striatum: F(3,8) = 33.01, P <0.01; U69,595/dorsal striatum: F(3,8) = 6.16, P <0.0001; U50,488/ventral striatum: F(3,8) = 105.7, P <0.0001 and U50,488/dorsal striatum: F(3,8) = 20.87, P <0.0004). Bonferroni’s post hoc test: *p <0.05; **p <0,01; ***p < 0.001 versus corresponding vehicles; ^^p < 0.001 versus U69,593 (10 μM); ††p <0.001 versus U50,488 (10 μM). B. The effects of Akt and CaMKII inhibition on KOR mediated reduction in SERT activity: Pretreatment of Akt X (20 μM) or KN93 (2 μM) for 45 min prior to U69,593 or U50,488 (10 μM, 15 min) treatment attenuated inhibitory effects of U69,593 or 50,488 on SERT activity (One-way ANOVA: F(5,46) = 18.57, P <0.0001). ***p <0.001 versus Vehicle + U69,593; ^^p <0,01, ^^^p <0.001 versus Vehicle + U50,488 (Bonferroni’s post hoc test). Vehicle contained both ethanol and buffer.