TABLE 2

Pharmacological properties of native or GFP-tagged coexpressed receptors

Saturation binding assays were performed using [¹²⁵I]DOI (5-HT_2B receptor) or [¹²⁵I]GTI (5-HT_1B receptor) on membrane fraction of cell homogenate (Membranes) or intact cells (Whole Cells) of the different stable clonal cell lines expressing the 5-HT_1B receptor and the 5-HT_2B receptor with or without tag. Binding data were analyzed using the iterative non-linear fitting software GraphPad Prism 2.0 to calculate dissociation constants (K_D) and maximum number of sites (B_max). Insertion of the various GFPs at the N-terminal part of the receptor did not affect receptor affinity. Intact cell B_max represents only about 60% of that of binding on membranes. Co-expression of the receptor subtypes did not alter the receptor affinity for GTI or DOI (Table 1). Values are means ± S.E. of three independent determinations in triplicate.