Adenosine A2a receptor (A2aR or ADORA2A) stably expressed in HEK-293 cells. A2aR is a member of the seven transmembrane G protein-coupled receptor (GPCR) family. The activity of A2aR is mediated by G?s protein which activates adenylyl cyclase, resulting in the synthesis of intracellular cAMP. The level of cAMP correlates with the respective adenosine (agonist) level, and the cell line can be used to measure the EC50 and IC50 values of A2aR agonists or antagonists in a quantitative manner. Binding of extracellular adenosine ligand or its stable analog NECA (5′-(N-Ethylcarboxamido) adenosine) to the A2aR expressed on the surface of this cell line induces cAMP expression.