Lack of role for dephosphorylation of GABABR2–S783 in METH-dependent decrease in IBaclofen in VTA DA neurons. A, Protocol for VTA GABA neurons. Single injection of METH in GABABR2–S783A KI mice. B, Mean IBaclofen (100 μm) in VTA GABA neurons is reduced 24 h after a single injection of METH (2 mg/kg, n = 21) compared with saline (0.9%, n = 23) (Padgett et al., 2012) in littermate controls. **p < 0.01 two-way ANOVA with Bonferroni post hoc test. In GABABR2–S783A KI mice, there was no decrement in IBaclofen after 1 d METH (n = 6 saline, n = 7 METH). C, Protocol for VTA DA neurons after 5 d injections of METH or saline in GABABR2–S783A KI mice. D, Mean IBaclofen (300 μm) is significantly reduced (24–48 h) in VTA DA neurons of GABABR2–S783A KI receiving 5 d METH (2 mg/kg, n = 14) compared with 5 d saline (0.9%, n = 19). **p < 0.05 unpaired t test. E, Mean IQuinpirole (30 μm) in VTA DA neurons from GABABR2–S783A KI mice with 5 d METH or 5 d saline treatments. F, Mean Ih in VTA DA neurons from GABABR2–S783A KI mice with 5 d METH or 5 d saline treatments.