Table 1.

Distribution of adenosine receptors in different tissues.

	Adenosine Receptors Distribution in Tissues
Level of Expression	A1	A2A	A2B	A3
High up	Brain (cortex, hippocampus, cerebellum, sheet spine, eyes, atria and adrenal gland (adrenal).	Thymus, leukocytes (lymphocytes and granulocytes), platelets, spleen, GABAergic and olfactory bulb.	Cecum, colon, bladder.	Mast cells, testis. (Rat)
Intermediate	Other brain regions, skeletal muscle, liver, kidney, adipose tissue, salivary glands, esophagus, colon, testis.	Heart, lung, blood vessels, peripheral nerves.	Lung, blood vessels, eyes, mast cells.	Cerebellum, hippocampus, microglial cells, lung, spleen, pineal.
Low	Lung (but probably high in bronchi), pancreas.	Other brain regions.	Adipose tissue, adrenal gland, brain, kidney, liver, ovary, pituitary gland.	Thyroid, other cerebral regions, adrenal gland, spleen (human), liver, kidney, heart, intestine, testes (human).

(Source: Modified from Fredholm [8]).