摘要：

After the recognition of the main physiological roles of the purine metabolites, Burnstock was the first to classify receptors of adenosine and its derivatives into P1 and P2 purinergic receptors (Burnstock, 1980). Adenosine activates the P1 receptors, while the ATP and ADP act on the P2 receptors. Not long ago four adenosine receptors subtypes have been defined based on structural, functional and pharmacological point of view, like A1, A2A, A2B and A3 receptors. To characterize the adenosine receptor subtypes there have been many aspects taken in view like the special pharmacological profile (the rank of order of potency of the different agonists and antagonists), their capacity binding to G-proteins, or the signal transduction mechanisms during the activation of the adenosine receptors. The International Union of Pharmacology (IUPHAR) take account of these approaches, being prescribed by the Committee on Receptor Nomenclature and Drug Classification. (Fredholm et al, 2001). All subtypes of the adenosine receptors have already been cloned. From chemical point of view these receptors are asparagine linked glycoproteins, in which the palmitoylation suitable site is in the next proximity of the terminal carboxyl molecule (excepting the A2A receptor) (Fredholm and Jacobson, 2001). The receptors are parts of the cell membranes linked to different G proteins structures. As IUPHAR recently admitted based on the phylogenetic analyses, the adenosine receptors linked to G proteins belong to the I. class of the „rhodopsin subtypes" (Poulsen and Quinn, 1998).

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