Adenosine receptor

The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. There are four known types of adenosine receptors in humans: A₁, A_2A, A_2B and A₃; each is encoded by a different gene.

The adenosine receptors are commonly known for their antagonists caffeine, theobromine, and theophylline, whose action on the receptors produces the stimulating effects of coffee, tea and chocolate.