Primary cells transiently transfected with the calcium biosensor i-Photina® from Lonza are available as a ready-to-use tool for drug discovery research. They are a groundbreaking robust (Z' ≥ 0.6) assay system for detecting intracellular Ca2+-dependent signaling upon stimulation with physiological agonists in high-throughput formats. This was demonstrated on a LUMIstar Omega microplate reader from BMG LABTECH for four different classes of G-protein coupled receptors in dose-dependent manners for two plate formats.