Baron B M, Harrison B L, McDonald I A, Meldrum B S, Palfreyman M G, Salituro F G, Siegel B W, Slone A L, Turner J P, White H S
Marion Merrell Dow Research Institute, Cincinnati, Ohio 45215.
J Pharmacol Exp Ther. 1992 Sep;262(3):947-56.
The N-methyl-D-aspartate (NMDA)-preferring glutamate receptor subtype possesses, in addition to the recognition site for glutamate, a binding site for glycine. We report here on the pharmacological properties of 3-(4,6-dichloro-2-carboxyindol-3-yl)-propionic acid (MDL 29,951) and 4-carboxymethylamino-5,7-dichloroquinoline-2-carboxylic acid (MDL 100,748), two novel glycine antagonists of NMDA receptor activation in vitro and in vivo. We have measured in parallel the effects of two previously described glycine antagonists, 7-chlorokynurenic acid and 5,7-dichlorokynurenic acid. All were potent inhibitors of [3H]glycine binding. Ki values (microM) were 0.36 (7-chlorokynurenic acid), 0.08 (5,7-dichlorokynurenic acid), 0.07 (MDL 100,748) and 0.14 (MDL 29,951). MDL 100,748 and MDL 29,951 were approximately 2000-fold selective for the glycine binding site relative to the glutamate recognition sites. All four compounds completely inhibited the use-dependent binding of [3H]N-[1-(2-thienyl) cyclohexyl]-piperidine and were noncompetitive, glycine-reversible inhibitors of both NMDA-induced biochemical and electrophysiological responses in brain slice preparations. A competitive interaction with the glycine binding site was also evident in that MDL 29,951 and MDL 100,748 produced parallel rightward shifts in the glycine requirement for demonstration of NMDA-stimulated elevations in cytosolic calcium in cultured neuronal preparations. The glycine antagonists were potent anticonvulsants after their i.c.v. administration to audiogenic seizure-susceptible DBA/2J mice. Because the compounds chosen encompass a variety of chemical structures, the results indicate that glycine is required for NMDA receptor activation and that bioavailable glycine antagonists may form the basis of a novel therapy for epilepsy.
除了谷氨酸识别位点外，N-甲基-D-天冬氨酸（NMDA）偏好型谷氨酸受体亚型还具有甘氨酸结合位点。我们在此报告3-(4,6-二氯-2-羧基吲哚-3-基)丙酸（MDL 29,951）和4-羧甲基氨基-5,7-二氯喹啉-2-羧酸（MDL 100,748）这两种新型甘氨酸拮抗剂在体外和体内对NMDA受体激活的药理学特性。我们同时测量了两种先前描述的甘氨酸拮抗剂7-氯犬尿氨酸和5,7-二氯犬尿氨酸的作用。所有这些都是[3H]甘氨酸结合的有效抑制剂。Ki值（微摩尔）分别为0.36（7-氯犬尿氨酸）、0.08（5,7-二氯犬尿氨酸）、0.07（MDL 100,748）和0.14（MDL 29,951）。相对于谷氨酸识别位点，MDL 100,748和MDL 29,951对甘氨酸结合位点的选择性约为2000倍。所有这四种化合物完全抑制了[3H]N-[1-(2-噻吩基)环己基]-哌啶的使用依赖性结合，并且在脑片制备中对NMDA诱导的生化和电生理反应均为非竞争性、甘氨酸可逆性抑制剂。MDL 29,951和MDL 100,748在培养的神经元制剂中对NMDA刺激的胞质钙升高所需的甘氨酸产生平行的右移，这也表明它们与甘氨酸结合位点存在竞争性相互作用。将这些甘氨酸拮抗剂经脑室内注射给对听源性癫痫敏感的DBA/2J小鼠后，它们是有效的抗惊厥剂。由于所选择的化合物涵盖了多种化学结构，结果表明甘氨酸是NMDA受体激活所必需的，并且可生物利用的甘氨酸拮抗剂可能构成一种新型癫痫治疗方法的基础。
