Figure 5.

The GB_1a proximal C-terminal domain does not affect baclofen-induced GB_1a/GB₂ receptor activation and cAMP inhibition. A, Dose–response curves of baclofen on GB_1a^CFP/GB₂^YFP FRET efficiency for GB_1a-WT (n = 10–21, N = 5, ED₅₀ = 0.82 ± 0.003 μm) and GB_1a-Δ21 (n = 11–21, N = 3–5, ED₅₀ = 0.58 ± 0.013 μm) proteins. E at 100 μm baclofen was set as 100%. B, Effect of 10 μm baclofen on CFP–Epac–YFP FRET efficiency (E_Epac), reporting cAMP level, in 1a^−/− boutons and in 1a^−/− boutons expressing GB_1a-WT or GB_1a-Δ21 proteins. Baclofen increased E_Epac in GB_1a-WT-expressing (n = 30–32, N = 6, *p < 0.05) and GB_1a-Δ21-expressing (n = 27–35, N = 5–6, *p < 0.05) boutons, but did not affect E_Epac in 1a^−/− boutons (n = 25–26, N = 5, p > 0.05) One-way ANOVA with post hoc Bonferroni's multiple-comparison tests indicated significance. Error bars indicate SEM.