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흰쥐 대뇌피질에서 A<sub>1</sub> 아데노신 수용체의 탈감작

Desensitization of A<sub>1</sub> Adenosine Receptors in Rat Cerebral Cortex

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Following the subcutaneous administration of R(-)N<sup>6</sup>-(2-phenylisopropyl)adenosine(600 nmol/kg/hr) to rats for 1 week using tAlzet<sup>??</sup> mini-osmotic pumps, A<sub>1</sub> adenosine receptor functions were determined using [<sup>3</sup>H]DPCPX binding, [<sup>35</sup>S]GTP<sub>γ</sub>S binding, and adenylyl cyclase assays. A<sub>1</sub> adenosine receptor binding and the inhibition of adenylyl cyclase activity by PIA was not altered in cerebrocortical membranes prepared from PIA-treated rats. However, there was a significant decrease in the A<sub>1</sub> adenosine receptor-mediated stimulation of [<sup>35</sup>S]GTP<sub>γ</sub>S binding to cerebrocortical membranes prepared from PIA-treated rats(22.0% decrease in basal activity; 19.7% decrease in maximal activity). These results suggest that the desensitization of A<sub>1</sub> adenosine receptors following chronic administration involves agonist-induced uncoupling of the receptors from G proteins rather than alteration of A<sub>1</sub> adenosine receptor molecules. It is also suggested that the determination of stimulation of [<sup>35</sup>S]GTP<sub>γ</sub>S binding to G proteins is a suitable tool in studying the receptor regulation including desensitization