Binding and biological activity of GR134056X and GR135470X at CCK1R and CCK2R. Shown are the data from competition-binding experiments with the orthosteric radioligand, 125I-CCK (A, D), or the allosteric radioligands, 125I-BDZ-1 or 2 (B, E) at the CCK1R (top panel) or the CCK2R (bottom panel) expressed on CHO membranes. Also shown are the intracellular calcium responses of these compounds at both subtypes of CCK receptors expressed on CHO-CCK1R and CHO-CCK2R cells (C, F). Data are represented as means ± S.E.M. from duplicate determinations from at least three independent experiments.