(A,C) Whole-cell recordings from VTA DA neurons show baclofen-activated GIRK currents (IBaclofen; 300 µM) from WT and SNX27DA KO mice. Extracellular Ba2+ (1 mM), a selective inhibitor of inwardly rectifying potassium channels (Kir), decreases IBaclofen. Outward current measured at −50 mV is plotted as a function of time. (B,D) Scatter plot of IBaclofen for indicated DA neurons. **p<0.01, one-way ANOVA with Bonferroni post hoc test.