The adenosine receptors (P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as endogenous ligand. In humans, there are four types of adenosine receptors(A1,A2A ,A2B,A3). Each is encoded by a separate gene and has different functions, although with some overlap. For instance, both A1 receptors and A2A play roles in the heart, regulating myocardial oxygen consumption and coronary blood flow, while the A2A receptor also has broader anti-inflammatory effects throughout the body. These two receptors also have important roles in the brain, regulating the release of other neurotransmitters such as dopamine and glutamate, while the A2B and A3 receptors are located mainly peripherally and are involved in processes such as inflammation and immune responses.