FIGURE 10.
D1R promotes GHS-R1a-GHS-R1b heteromers coupling to Gs/olf protein. cAMP accumulation was determined in HEK-293T cells transfected with GHS-R1b-Rluc cDNA (0.2 μg), GHS-R1a-YFP cDNA (1 μg), and D1R cDNA (0.4 μg, A and D) or D2R cDNA (0.4 μg, B) or single-transfected with the same amount of the indicated receptors (C). Cells were incubated overnight with vehicle, PTX (10 ng/ml), or the Gαq inhibitor YM254890 (YM, 1 μm) or for 2 h with CTX (100 ng/ml) and pretreated (15 min) with vehicle, the GHS-R1a antagonist YIL781 (YIL, 2 μm), or the D1R antagonist SCH23390 (SCH, 1 μm), followed by activation (15 min) with ghrelin (100 nm), the D1R agonist SKF81297 (SKF, 100 nm), or the D2R agonist quinpirole (Quin, 1 μm) alone or in combination in the absence (A and D) or presence (B and C) of forskolin (FK, 0.5 μm). Values are means ± S.E. of six to eight experiments and expressed as percentage of values of cells not treated with ghrelin (100%, dotted line). Statistical differences between differently treated cells were analyzed by ANOVA followed by Bonferroni's corrections. *, p < 0.05; **, p < 0.01 compared with vehicle-treated cells.