Fig. 6.

Inhibition of cell-surface Bgt binding by different ligands. A, Inhibition of the initial rate of¹²⁵I-Bgt binding to cell-surface PC12 BgtRs by the agonists ACh (solid circle), carbachol (solid square), nicotine (solid diamond), cytisine (solid triangle), and the antagonists MLA (open triangle) and dTC (open square). Plotted inA and B is the fraction of maximum¹²⁵I-Bgt bound, i.e., ¹²⁵I-Bgt bound in the presence of ligand divided by ¹²⁵I-Bgt bound in the absence of ligand, as a function of ligand concentration. Theline through the points represents a least-squares fit to the data of the equation: fraction of maximum ¹²⁵I-Bgt bound = (Max.)/(1 + ([ligand]/IC₅₀))ⁿ, where ⁿis the Hill coefficient and Max. is the maximum fitted value. The results for all experiments are summarized in Table 2.B, Inhibition of the initial rate of¹²⁵I-Bgt binding to cell-surface α7/5HT3 homomers by the agonists ACh (solid circle), carbachol (solid square), nicotine (solid diamond), cytisine (solid triangle), and the antagonists MLA (open triangle) and dTC (open square).