Antagonist-radioligand binding to D_2L-receptors in intact cells

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• 作者：Ann Packeu ; Jean-Paul De Backer ; Isabelle Van Liefde ; Patrick M.L. V ; erheyden ; Georges Vauquelin
• 关键词：Dopamine receptor ; Radioligand binding ; Intact cells ; Raclopride ; Spiperone
• 刊名：Biochemical Pharmacology
• 出版年：2008
• 期刊代码：2_00062952
• 类别：pha
• 出版时间：1 June 2008
• 卷：75
• 期：11
• 页码：2192-2203
• 文件大小：376 K

摘要

D₂-dopamine receptors mediate most of the physiological actions of dopamine and are important recognition sites for antipsychotic drugs. Earlier binding studies were predominantly done with broken cell preparations with the tritiated D₂-receptor antagonists [³H]-raclopride, a hydrophilic benzamide, and [³H]-spiperone, a highly hydrophobic butyrophenone. Here we compared [³H]-raclopride and [³H]-spiperone binding properties in intact Chinese Hamster Ovary cells stably expressing recombinant human D_2L-receptors. Specific binding of both radioligands occurred to a comparable number of sites. In contrast to the rapid dissociation of [³H]-raclopride in both medium only and in the presence of an excess of unlabelled ligand [³H]-spiperone dissociation was only observed in the latter condition, and it was still slower than in broken cell preparations. However, this could not explain the pronounced difference in the potency of some unlabelled ligands to compete with both radioligands. To integrate these new findings, a model is proposed in which raclopride approaches the receptor from the aqueous phase, while spiperone approaches the receptor by lateral diffusion within the membrane.