Time-resolved quantitative analysis of CCK1 receptor-induced intracellular calcium increase

► We set up a cell-based bioassay to screen for peptides with CCK1-receptor activity. ► A plate reader and a confocal microscope were compared to measure the Ca2+ increase. ► The plate reader assay allowed fast, high throughput screening. ► The microscope identified single-cell variations and factors reducing specificity. ► Both methods proved complementary to become a sensitive and selective assay.