Figure 2.

Agonist-induced activation of SRE via 5-HT₇ receptor. A, Dose-dependent activation of SRE by serotonin in the NIH3T3 cells expressing the 5-HT₇ receptor. NIH3T3 cells seeded onto 24-well plates were transfected with 100 ng of 5-HT₇ receptor cDNA, 50 ng of pSRE.L, and 50 ng of pCMV-β-gal vectors. Twenty-four hours after transfection, cells were serum-starved for 16 h and stimulated with indicated concentrations of serotonin for 6 h. Thereafter, activity of SRE was determined. Presented data are the mean ± SEM(n = 4). B, The 5-HT₇ receptor activates SRE in a ligand-independent manner. Indicated amounts of the 5-HT₇ receptor cDNA were transfected into NIH3T3 cells together with 50 ng of pSRE.L and 50 ng of pCMV-β-gal, and SRE activity was determined. Data points represent the means ± SEM from at least three independent experiments. C, An inverse agonist inhibits 5-HT₇ receptor-induced SRE activation. NIH3T3 cells seeded onto 24-well plates were transfected as described in A. Twenty-four hours after transfection, cells were serum-starved for 16 h and treated with 100 nm methysergide. Data points represent the means ± SEM (n = 4). A statistically significant difference between values is indicated (^*p < 0.01).