| Popis: |
It is well known that the nucleoside adenosine exerts a modulatory influence in the central nervous system by activating G protein coupled receptors. Adenosine A 2A receptors, the subject of the present review, are predominantly expressed in striatum, the major area of the basal ganglia. Activation of A 2A receptors interferes with effects mediated by most of the principal neurotransmitters in striatum. In particular, the inhibitory interactions between adenosine acting on A 2A receptors and dopamine acting on D 2 receptors have been well examined and there is much evidence that A 2A receptors may be a possible target for future development of drugs for treatment of Parkinson's disease, schizophrenia and affective disorders. Our understanding of the role of striatal A 2A receptors has increased dramatically over the last few years. New selective antibodies, antagonist radioligands and optimized in situ hybridization protocols have provided detailed information on the distribution of A 2A receptors in rodent as well as primate striatum. Studies on the involvement of A 2A receptors in the regulation of DARPP-32 and the expression of immediate early genes, such as nerve growth factor-induced clone A and c- fos , have pointed out an important role for these receptors in regulating striatopallidal neurotransmission. Moreover, by using novel selective antagonists for A 2A receptors and transgenic mice lacking functional A 2A receptors, crucial information on the behavioral role of striatal A 2A receptors has been provided, especially concerning their involvement in the stimulatory action of caffeine and the anti-Parkinsonian properties of A 2A receptor antagonists. In the present review, current knowledge on the distribution, biochemistry and function of striatal A 2A receptors is summarized. |
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