G protein coupled receptors (GPCR) are one of the largest receptor classes targeted by drug discovery programs. Calcium flux (coupled via Gq pathway) assay is a preferred method in drug discovery for screening GPCR targets. However, over 60% of the known GPCRs signal through adenylyl cyclase activity coupled to cAMP. Most of the existing cAMP assays not only require cell lysis but also lack both temporal and spatial resolution. Screen Quest Live Cell cAMP Assay Service Pack provides the real-time monitoring of intracellular cAMP change in a high-throughput format without a cell lysis step. The assay works through the cell lines that contain either an exogenous cyclic nucleotide-gated channel(CNGC) or the promiscuous G-protein, Gα16. The channel is activated by elevated levels of intracellular cAMP, resulting in ion flux and cell membrane depolarization which can be detected with either a fluorescent calcium (such as Quest Fluo-8 AM) or a fluorescent membrane potential dye. Co-expression of Gα16with specific non-Gq-coupled receptors will result in the generation of an intracellular calcium signal upon receptor stimulation. The Screen Quest Live Cell cAMP Assay Service Pack provides both cell lines and reagents for the measurement of intracellular cAMP changes with a FLIPR, a FDSS or other equivalent fluorescence microplate readers. It has been successfully used to measure Gs and Gi coupled GPCR activity.