Pharmacological Characterization of<i>N</i>,<i>N</i>-Dimethyl-2-(2-amino-4-methylphenyl thio)benzylamine as a Ligand of the Serotonin Transporter with High Affinity and Selectivity
作者:Sylvie Chalon、Jari Tarkiainen、Lucette Garreau、Hakan Hall、Patrick Emond、Johnny Vercouillie、Lars Farde、Philippe Dasse、Katarina Varnas、Jean-Claude Besnard、Christer Halldin、Denis Guilloteau
DOI:10.1124/jpet.102.042226
日期:2003.1.1
Serotonin transporter has a key-role in regulation of serotoninergic function, and is involved in numerous neurodegenerative and psychiatric disorders. To obtain an efficient radioactive ligand allowing the study of this transporter in vitro and in vivo, we synthesized a new diphenyl sulfide derivative, N , N -dimethyl-2-(2-amino-4-methylphenylthio)benzylamine or MADAM. We present here extensive pharmacological characterization of this compound. [3H]MADAM bound to serotonin transporters with a very high affinity in vitro on rat cortical membranes, at least 2 times better than the most commonly used radioactive probes ( K d, 60 pM; B max, 543 fmol/mg of protein). Competition studies showed few inhibitory effect of nisoxetine ( K i = 270 nM), no inhibitory effect of desipramine or 1-[2-(diphenylmethoxy) ethyl]-4-(3-phenylpropyl)piperazine (GBR 12935) ( K i >1000 nM), and strong effect of paroxetine ( K i = 0.32 nM) and citalopram ( K i = 1.57 nM). Therefore, MADAM has around 1000-fold better selectivity for the serotonin transporter than for other transporters. Autoradiographic studies both on rat and postmortem human brain slices demonstrated that the distribution of [3H]MADAM parallels the localization of serotonin transporters and is prevented by known inhibitors of them. The high affinity and selectivity of [3H]MADAM for the serotonin transporter show that it is very valuable for studies using in vitro approaches. The high selectivity and low nonspecific binding of [3H]MADAM on the postmortem human brain, together with preliminary in vivo results with [11C]MADAM, is a new argument for future use of this ligand in in vivo studies of the distribution, pharmacology, and pathophysiology of the serotonin transporter in the human brain with positron emission tomography.
羟色胺转运体在调节羟色胺能功能方面起着关键作用,并与多种神经退行性疾病和精神疾病有关。为了获得一种高效的放射性配体,以便对这种转运体进行体外和体内研究,我们合成了一种新的二苯硫醚衍生物 N , N -二甲基-2-(2-氨基-4-甲基苯硫基)苄胺或 MADAM。我们在此对该化合物进行了广泛的药理学表征。体外实验中,[3H]MADAM 与大鼠大脑皮层膜上的血清素转运体结合的亲和力非常高,比最常用的放射性探针至少高出 2 倍(K d,60 pM;B max,543 fmol/mg 蛋白质)。竞争研究表明,尼索西汀的抑制作用很小(K i = 270 nM),地西帕明或 1-[2-(二苯基甲氧基)乙基]-4-(3-苯基丙基)哌嗪(GBR 12935)没有抑制作用(K i >1000 nM),而帕罗西汀(K i = 0.32 nM)和西酞普兰(K i = 1.57 nM)的抑制作用很强。因此,MADAM 对血清素转运体的选择性比对其他转运体的选择性高出约 1000 倍。对大鼠和死后人类大脑切片进行的自显影研究表明,[3H]MADAM 的分布与血清素转运体的定位相似,并且能被已知的血清素转运体抑制剂所阻止。[3H]MADAM对5-羟色胺转运体的高亲和力和选择性表明,它对使用体外方法进行研究非常有价值。[3H]MADAM对死后人脑的高选择性和低非特异性结合,以及[11C]MADAM在体内的初步结果,为今后利用正电子发射断层扫描技术在体内研究血清素转运体在人脑中的分布、药理学和病理生理学提供了新的论据。