Shown are the intracellular calcium responses of these compounds at both subtypes of CCK receptors expressed on CHO-CCK1R (top row) and CHO-CCK2R (bottom row) cells (A, D). Also shown are the data from competition-binding experiments with the orthosteric radioligand, 125I-CCK (B, E), or the allosteric radioligands, 125I-BDZ-1 or 2 (C, F) at the CCK1R or the CCK2R expressed on CHO membranes respectively. The X-axis values reflect the absence of ligand (0) to the left of the break, and log molar concentrations to the right of the break. Biological activity data are represented as percentages of the maximal responses of each cell line to 10 nM concentration of natural agonist, CCK. Non-saturable binding was determined by using 1 μM unlabeled BDZ or CCK. Data are represented as means ± S.E.M. from duplicate determinations from at least five independent experiments.