Kohara Atsuyuki, Toya Takashi, Tamura Seiji, Watabiki Tomonari, Nagakura Yukinori, Shitaka Yoshitsugu, Hayashibe Satoshi, Kawabata Shigeki, Okada Masamichi
Neuroscience Research, Pharmacology Laboratories, Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Ltd., 21 Miyukigaoka, Tsukuba, 305-8585, Japan.
J Pharmacol Exp Ther. 2005 Oct;315(1):163-9. doi: 10.1124/jpet.105.087171. Epub 2005 Jun 23.
Metabotropic glutamate receptor type 1 (mGluR1) is thought to play important roles in the neurotransmission and pathogenesis of several neurological disorders. Here, we describe the radioligand binding properties and pharmacological effects of a newly synthesized, high-affinity, selective, and noncompetitive mGluR1 antagonist, 6-amino-N-cyclohexyl-N,3-dimethylthiazolo[3,2-a]benzimidazole-2-carboxamide (YM-298198). YM-298198 inhibited glutamate-induced inositol phosphate production in mGluR1-NIH3T3 cells with an IC50 of 16 +/- 5.8 nM in a noncompetitive manner. Its radiolabeled form, [3H]YM-298198, bound to mGluR1-NIH3T3 cell membranes with a KD of 32 +/- 8.5 nM and a Bmax of 2297 +/- 291 fmol/mg protein. In ligand displacement experiments using rat cerebellum membrane, an existing noncompetitive mGluR1 antagonist 7-(hydroxyimino)cyclo-propa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt) competitively displaced [3H]YM-298198 binding, although glutamate and other mGluR1 ligands acting on a glutamate site failed to inhibit [3H]YM-298198 binding, suggesting that YM-298198 binds to CPCCOEt (allosteric) binding sites but not to glutamate (agonist) binding sites. Specificity was demonstrated for mGluR1 over mGluR subtypes 2 to 7, ionotropic glutamate receptors, and other receptor, transporter, and ion channel targets. In in vivo experiments, orally administered YM-298198 showed a significant analgesic effect in streptozotocin-induced hyperalgesic mice at doses (30 mg/kg) that did not cause Rotarod performance impairment, indicating that it is also useful even for in vivo experiments. In conclusion, YM-298198 is a newly synthesized, high-affinity, selective, and noncompetitive antagonist of mGluR1 that will be a useful pharmacological tool due to its highly active properties in vitro and in vivo. Its radiolabeled form [3H]YM-298198 will also be a valuable tool for future investigation of the mGluR1.
代谢型谷氨酸受体1（mGluR1）被认为在几种神经疾病的神经传递和发病机制中发挥重要作用。在此，我们描述了一种新合成的、高亲和力、选择性和非竞争性的mGluR1拮抗剂6-氨基-N-环己基-N,3-二甲基噻唑并[3,2-a]苯并咪唑-2-甲酰胺（YM-298198）的放射性配体结合特性和药理作用。YM-298198以非竞争性方式抑制mGluR1-NIH3T3细胞中谷氨酸诱导的肌醇磷酸生成，IC50为16±5.8 nM。其放射性标记形式[3H]YM-298198与mGluR1-NIH3T3细胞膜结合，KD为32±8.5 nM，Bmax为2297±291 fmol/mg蛋白。在使用大鼠小脑膜的配体置换实验中，现有的非竞争性mGluR1拮抗剂7-（羟基亚氨基）环丙烷[b]色烯-1a-羧酸乙酯（CPCCOEt）竞争性置换[3H]YM-298198的结合，尽管谷氨酸和作用于谷氨酸位点的其他mGluR1配体未能抑制[3H]YM-298198的结合，这表明YM-298198与CPCCOEt（变构）结合位点结合，但不与谷氨酸（激动剂）结合位点结合。已证明YM-298198对mGluR1相对于mGluR亚型2至7、离子型谷氨酸受体以及其他受体、转运体和离子通道靶点具有特异性。在体内实验中，口服给药的YM-298198在链脲佐菌素诱导的痛觉过敏小鼠中，在不引起转棒试验性能受损的剂量（30 mg/kg）下显示出显著的镇痛作用，表明它甚至对体内实验也有用。总之，YM-298198是一种新合成的、高亲和力、选择性和非竞争性的mGluR1拮抗剂，由于其在体外和体内的高活性特性，将成为一种有用的药理学工具。其放射性标记形式[3H]YM-298198也将成为未来研究mGluR1的有价值工具。
