Patel S, Patel S, Marwood R, Emms F, Marston D, Leeson P D, Curtis N R, Kulagowski J J, Freedman S B
Department of Biochemistry and Molecular Biology, Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, UK.
Mol Pharmacol. 1996 Dec;50(6):1658-64.
We identified a novel azaindole derivative, L-750,667, that has high affinity (Ki = 0.51 nM) and >2000-fold selectivity for D4 dopamine receptors compared with its activity at D2 and D3 dopamine receptors. L-750,667 had little affinity for rat D1/D5 dopamine receptors, sigma binding sites, or 5-hydroxytryptamine1A or 5-hydroxytryptamine2 receptors. In functional studies, L-750,667 exhibited high affinity antagonist activity at D4 receptors, reversing dopamine (1 microM)-induced inhibition of cAMP accumulation in human embryonic kidney (HEK) cells expressing the human D4 receptor (hD4 HEK) with an EC50 value of 80 nM. The radioiodinated form of L-750,667 bound specifically to the human dopamine D4 receptor expressed in HEK cells and saturation analysis revealed a single high affinity binding site for [125I]L-750,667 (Kd = 0.16 +/- 0.06 nM). The maximum number of binding sites (Bmax) estimated using [125I]L-750,667 in hD4 HEK cells was 251 +/- 71 fmol/mg, which correlated well with the Bmax value determined using [3H]spiperone (227 +/- 83 fmol/mg) in the same membrane preparations. The pharmacological profile of [125I]L-750,667 binding to hD4 HEK cells was evaluated using known dopamine receptor agonists and antagonists. The rank order of potencies for dopamine receptor agonists was dopamine > quinpirole > 6,7-aminodihydroxytetralin > 5,6-aminodihydroxytetralin. Dopamine receptor antagonists also showed high affinity, with a rank order of haloperidol > chlorpromazine > domperidone > (+)-butaclamol > (-)-sulpiride = (+)-sulpiride > (+)-SCH23390 > (-)-butaclamol. [125I]L-750,667, bound to D4 receptors in a stereoselective manner with (+)-butaclamol showing higher activity than its respective enantiomer (-)-butaclamol. These results show that [125I]L-750,667 is a novel, highly selective radioligand for dopamine D4 receptors and may be used to investigate the dopamine D4 receptor population in the central nervous system.
我们鉴定出一种新型氮杂吲哚衍生物L-750,667，它对D4多巴胺受体具有高亲和力（Ki = 0.51 nM），与它对D2和D3多巴胺受体的活性相比，对D4多巴胺受体的选择性大于2000倍。L-750,667对大鼠D1/D5多巴胺受体、σ结合位点或5-羟色胺1A或5-羟色胺2受体几乎没有亲和力。在功能研究中，L-750,667在D4受体上表现出高亲和力拮抗剂活性，可逆转多巴胺（1 μM）诱导的表达人D4受体（hD4 HEK）的人胚肾（HEK）细胞中cAMP积累的抑制，其EC50值为80 nM。L-750,667的放射性碘化形式特异性结合于HEK细胞中表达的人多巴胺D4受体，饱和分析显示[125I]L-750,667有一个单一的高亲和力结合位点（Kd = 0.16 +/- 0.06 nM）。在hD4 HEK细胞中使用[125I]L-750,667估计的最大结合位点数（Bmax）为251 +/- 71 fmol/mg，这与在相同膜制剂中使用[3H]螺哌隆测定的Bmax值（227 +/- 83 fmol/mg）相关性良好。使用已知的多巴胺受体激动剂和拮抗剂评估了[125I]L-750,667与hD4 HEK细胞结合的药理学特征。多巴胺受体激动剂的效价顺序为多巴胺>喹吡罗> 6,7-氨基二羟基四氢萘> 5,6-氨基二羟基四氢萘。多巴胺受体拮抗剂也显示出高亲和力，其顺序为氟哌啶醇>氯丙嗪>多潘立酮>（+）-布他拉莫>（-）-舒必利=（+）-舒必利>（+）-SCH23390>（-）-布他拉莫。[125I]L-750,667以立体选择性方式结合到D4受体上，（+）-布他拉莫的活性高于其对映体（-）-布他拉莫。这些结果表明，[125I]L-750,667是一种新型的、高度选择性的多巴胺D4受体放射性配体，可用于研究中枢神经系统中的多巴胺D4受体群体。
