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, A2A, A2B and A3; each is encoded by a different gene.
The adenosine receptors are commonly known for their antagonists caffeine, theophylline, and theobromine, whose action on the receptors produces the stimulating effects of coffee, tea and chocolate. |