Thomet U, Baur R, Razet R, Dodd R H, Furtmüller R, Sieghart W, Sigel E
Department of Pharmacology, University of Bern, CH-3010 Bern, Switzerland.
Br J Pharmacol. 2000 Oct;131(4):843-50. doi: 10.1038/sj.bjp.0703558.
(+)-ROD188 was synthesized in the search for novel ligands of the GABA binding site. It shares some structural similarity with bicuculline. (+)-ROD188 failed to displace [(3)H]-muscimol in binding studies and failed to induce channel opening in recombinant rat alpha1beta2gamma2 GABA(A) receptors functionally expressed in Xenopus oocytes. (+)-ROD188 allosterically stimulated GABA induced currents. Displacement of [(3)H]-Ro15-1788 indicated a low affinity action at the benzodiazepine binding site. In functional studies, stimulation by (+)-ROD188 was little sensitive to the presence of 1 microM of the benzodiazepine antagonist Ro 15-1788, and (+)-ROD188 also stimulated currents mediated by alpha1beta2, indicating a major mechanism of action different from that of benzodiazepines. Allosteric stimulation by (+)-ROD188 was similar in alpha1beta2N265S as in unmutated alpha1beta2, while that by loreclezole was strongly reduced. (+)-ROD188 also strongly stimulated currents elicited by either pentobarbital or 5alpha-pregnan-3alpha-ol-20-one (3alpha-OH-DHP), in line with a mode of action different from that of barbiturates or neurosteroids as channel agonists. Stimulation by (+)-ROD188 was largest in alpha6beta2gamma2 (alpha6beta2gamma2>>alpha1beta2gamma2=alpha5beta2gamma2++ +>alpha2beta2ga mma2= alpha3beta2gamma2), indicating a unique subunit isoform specificity. Miniature inhibitory postsynaptic currents (mIPSC) in cultures of rat hippocampal neurons, caused by spontaneous release of GABA showed a prolonged decay time in the presence of 30 microM (+)-ROD188, indicating an enhanced synaptic inhibitory transmission.
(+)-ROD188是在寻找GABA结合位点的新型配体过程中合成的。它与荷包牡丹碱有一些结构相似性。在结合研究中，(+)-ROD188未能取代[(3)H]-蝇蕈醇，并且在非洲爪蟾卵母细胞中功能性表达的重组大鼠α1β2γ2 GABA(A)受体中未能诱导通道开放。(+)-ROD188变构性地刺激GABA诱导的电流。[(3)H]-Ro15-1788的取代表明其对苯二氮䓬结合位点具有低亲和力作用。在功能研究中，(+)-ROD188的刺激对1 microM苯二氮䓬拮抗剂Ro 15-1788的存在不太敏感，并且(+)-ROD188还刺激了由α1β2介导的电流，表明其主要作用机制与苯二氮䓬不同。(+)-ROD188在α1β2N265S中的变构刺激与未突变的α1β2相似，而洛来佐利的变构刺激则强烈降低。(+)-ROD188还强烈刺激了由戊巴比妥或5α-孕烷-3α-醇-20-酮(3α-OH-DHP)引发的电流，这与巴比妥类药物或神经甾体作为通道激动剂的作用方式不同。(+)-ROD188在α6β2γ2中的刺激最大(α6β2γ2>>α1β2γ2=α5β2γ2++ +>α2β2γ2=α3β2γ2)，表明其具有独特的亚基异构体特异性。大鼠海马神经元培养物中由GABA自发释放引起的微小抑制性突触后电流(mIPSC)在存在30 microM(+)-ROD188时显示出延长的衰减时间，表明突触抑制性传递增强。
