Block of Delayed-Rectifier Potassium Channels by Reduced Haloperidol and Related Compounds in Mouse Cortical Neurons
作者:Shi-Bing Yang、Felix Major、Lutz F. Tietze、Marjan Rupnik
DOI:10.1124/jpet.105.086561
日期:2005.10
Haloperidol is known as an antagonist of dopamine D2 receptors. However, it also blocks a variety of ion channels at concentrations above the therapeutic range. Reduced haloperidol (R-haloperidol), one of the main metabolites of haloperidol, has been reported to accumulate in certain tissues, particularly in brain cortex, and it may produce the pharmacological effects associated with haloperidol treatment. In this study, we assessed the effect of R-haloperidol and other related compounds on native delayed-rectifier potassium channels (KDR) in mouse cortical neurons by using the whole-cell patch-clamp technique. Although R-haloperidol has much lower affinity to D2 receptors than haloperidol, the IC50 of R-haloperidol to block KDR currents was 4.4 μM, similar to its parent compound. The binding site of R-haloperidol is on the cytoplasmic side of the channel because its quaternary derivative preferentially inhibited the currents from intracellular side. 4-Chlorophenyl-4-hydroxypiperidine (4C4HP) is the active fragment of haloperidol because other compounds containing this moiety, including L-741,626 (3-[4-(4-chlorophenyl)-4-hydroxypiperidin-l-yl]-methyl-1 H -indole) and loperamide, also blocked KDR channels. The potency of the 4C4HP fragment positively correlated with the hydrophobicity index (clogP) of the compounds tested. We conclude that R-haloperidol is a KDR channel blocker, although it does not interfere with the normal channel function at a clinically relevant concentration.
众所周知,氟哌啶醇是多巴胺 D2 受体的拮抗剂。然而,当浓度超过治疗范围时,它还会阻断多种离子通道。据报道,氟哌啶醇的主要代谢产物之一--还原型氟哌啶醇(R-haloperidol)会在某些组织中蓄积,尤其是在大脑皮层中,它可能会产生与氟哌啶醇治疗相关的药理作用。在这项研究中,我们采用全细胞贴片钳技术评估了R-氟哌啶醇及其他相关化合物对小鼠大脑皮层神经元中原生延迟整流钾通道(KDR)的影响。尽管R-氟哌啶醇对D2受体的亲和力远低于氟哌啶醇,但R-氟哌啶醇阻断KDR电流的IC50为4.4 μM,与其母体化合物相似。R-氟哌啶醇的结合位点在通道的细胞质一侧,因为其季衍生物优先抑制细胞内侧的电流。4-氯苯基-4-羟基哌啶(4C4HP)是氟哌啶醇的活性片段,因为含有该分子的其他化合物,包括 L-741,626 (3-[4-(4-氯苯基)-4-羟基哌啶-l-基]-甲基-1 H -吲哚)和洛哌酰胺,也能阻断 KDR 通道。4C4HP 片段的效力与测试化合物的疏水指数(clogP)呈正相关。我们的结论是,R-氟哌啶醇是一种 KDR 通道阻断剂,尽管它在临床相关浓度下不会干扰正常的通道功能。