Fig. (5) Comparison of agonist and antagonist activities determined in IP-One and intracellular calcium assays. (a) Concentration responses of carbachol. (b) Concentration-responses of muscarinic acetylcholine antagonists. The EC80 amount of agonist, carbachol, was used in both assays (5 μM for the IP-One assay and 0.1 μM for the intracellular calcium assay).