Freedman S B, Patel S, Marwood R, Emms F, Seabrook G R, Knowles M R, McAllister G
Merck Sharp and Dohme Research Laboratories, Neuroscience Research Centre, Essex, Great Britain.
J Pharmacol Exp Ther. 1994 Jan;268(1):417-26.
Binding of dopamine receptor ligands to human D2 and D3 receptors was characterized in Chinese hamster ovary (CHO) cells using the dopamine D2 receptor antagonist [125I] iodosulpiride. Only limited binding selectivity was observed for known dopamine D2 receptor antagonists from a variety of chemical classes, which included haloperidol, chlorpromazine, sulpiride, pimozide and cis flupenthixol. The most selective compound from this group were (+)butaclamol and domperidone which showed 5-fold D3 selectivity. A number of high affinity dopamine receptor agonists, including apomorphine and bromocriptine, also failed to demonstrate selectivity. In contrast, the natural ligand dopamine and the efficacious synthetic agonists quinpirole, (+)4-propyl-9-hydroxynapthoxazine (PHNO), 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN), 7-OH DPAT and N-0434 showed marked apparent human dopamine D3 (hD3) receptor selectivity. In the aminotetralin series, this selectivity was observed preferentially with analogs of the 6,7-rotamer compared with compounds from the 5,6-rotamer series. Functional coupling of the hD3 receptor was investigated in a number of cell lines in which the hD3 receptor was stably expressed, including CHO cells, the neuroblastoma-glioma hybrid cell line NG108-15 and a rat 1 fibroblast cell line. There was no evidence of functional coupling of the hD3 receptor to adenylate cyclase, arachidonic acid release, phospholipase C activation, K+ currents or calcium mobilization in any of the cell lines examined. Furthermore, guanine nucleotides failed to inhibit the binding of [3H] N-0437 to hD3 receptors in any of the three cell lines. There may be a number of explanations for these results. These cell lines may not have the appropriate G-protein or secondary messenger systems that are coupled to the hD3 receptor in situ. Alternatively, this receptor may couple by a mechanism that is as yet undefined. The finding that a wide range of structurally diverse human dopamine D2 (hD2) receptor agonists have an apparent hD3 selectivity may imply that the hD3 receptor exists predominantly in a high affinity state.
使用多巴胺D2受体拮抗剂[125I] 碘舒必利，在中国仓鼠卵巢（CHO）细胞中对多巴胺受体配体与人D2和D3受体的结合特性进行了研究。对于来自各种化学类别的已知多巴胺D2受体拮抗剂，仅观察到有限的结合选择性，这些拮抗剂包括氟哌啶醇、氯丙嗪、舒必利、匹莫齐特和顺式氟奋乃静。该组中选择性最高的化合物是（+）丁酰苯和多潘立酮，它们表现出5倍的D3选择性。许多高亲和力多巴胺受体激动剂，包括阿扑吗啡和溴隐亭，也未能表现出选择性。相比之下，天然配体多巴胺以及有效的合成激动剂喹吡罗、（+）4-丙基-9-羟基萘并恶嗪（PHNO）、2-氨基-6,7-二羟基-1,2,3,4-四氢萘（6,7-ADTN）、7-OH DPAT和N-0434表现出明显的人多巴胺D3（hD3）受体选择性。在氨基四氢萘系列中，与5,6-旋转异构体系列的化合物相比，在6,7-旋转异构体的类似物中优先观察到这种选择性。在多种稳定表达hD3受体的细胞系中研究了hD3受体的功能偶联，这些细胞系包括CHO细胞、神经母细胞瘤-胶质瘤杂交细胞系NG108-15和大鼠1成纤维细胞系。在所检测的任何细胞系中，均没有证据表明hD3受体与腺苷酸环化酶、花生四烯酸释放、磷脂酶C激活、K+电流或钙动员存在功能偶联。此外，鸟嘌呤核苷酸未能抑制[3H] N-0437与三种细胞系中任何一种的hD3受体的结合。对于这些结果可能有多种解释。这些细胞系可能没有与原位hD3受体偶联的合适G蛋白或第二信使系统。或者，该受体可能通过一种尚未明确的机制进行偶联。广泛的结构多样的人多巴胺D2（hD2）受体激动剂具有明显的hD3选择性这一发现可能意味着hD3受体主要以高亲和力状态存在。
