Fig. 7.

IP production and radioligand binding in HEK293 cells expressing 5-HT_2C receptors. (A) IP production was measured for 60 minutes in the presence of serum-free culture media (basal), 50 nM 5-HT, 10 μM Cab, or 25 nM Erg. The concentration of each drug was 20-fold over its EC₅₀ value. Basal levels of IP production were typically 14% of maximal stimulation with 5-HT. Data represent the mean ± S.E.M. from six experiments. (B) Cells were pretreated in the presence of serum-free culture media (basal), 50 nM 5-HT, 10 μM Cab, or 25 nM Erg for 60 minutes. Following drug washout, IP production was measured in serum-free culture media without drugs for 60 minutes. Data are expressed as the percentage of maximal IP production achieved with each drug, with basal IP levels subtracted out. Data represent the mean ± S.E.M. from six experiments. *P < 0.01 versus 5-HT. (C) Whole-cell radioligand binding assay. Cells were pretreated for 60 minutes with 50 nM 5-HT, 10 μM Cab, or 25 nM Erg. Following drug washout, cells were labeled with 2.5 nM [³H]mesulergine in the absence and presence of 1 μM 5-HT to define specific binding to cell surface 5-HT_2C receptors. Data are expressed as the percent inhibition of specific binding. Data represent the mean ± S.E.M. from four experiments. *P < 0.01 versus 5-HT.