A Substituted Anilino Enaminone Acts as a Novel Positive Allosteric Modulator of GABA<sub>A</sub> Receptors in the Mouse Brain
作者:Ze-Jun Wang、Liqin Sun、Patrice L. Jackson、Kenneth R. Scott、Thomas Heinbockel
DOI:10.1124/jpet.110.173740
日期:2011.3
A small library of anilino enaminones was analyzed for potential anticonvulsant agents. We examined the effects of three anilino enaminones on neuronal activity of output neurons, mitral cells (MC), in an olfactory bulb brain slice preparation using whole-cell patch-clamp recording. These compounds are known to be effective in attenuating pentylenetetrazol-induced convulsions. Among the three compounds tested, 5-methyl-3-(4-trifluoromethoxy-phenylamino)-cyclohex-2-enone (KRS-5Me-4-OCF3) showed potent inhibition of MC activity with an EC50 of 24.5 μM. It hyperpolarized the membrane potential of MCs accompanied by suppression of spontaneous firing. Neither ionotropic glutamate receptor blockers nor a GABAB receptor blocker prevented the KRS-5Me-4-OCF3-evoked inhibitory effects. In the presence of GABAA receptor antagonists, KRS-5Me-4-OCF3 completely failed to evoke inhibition of MC spiking activity, suggesting that KRS-5Me-4-OCF3-induced inhibition may be mediated by direct action on GABAA receptors or indirect action through the elevation of tissue GABA levels. Neither vigabatrin (a selective GABA-T inhibitor) nor 1,2,5,6-tetrahydro-1-[2-[[(diphenylmethylene)amino]oxy]ethyl]-3-pyridinecarboxylic acid hydrochloride (NNC-711) (a selective inhibitor of GABA uptake by GABA transporter 1) eliminated the effect of KRS-5ME-4-OCF3 on neuronal excitability, indicating that the inhibitory effect of the enaminone resulted from direct activation of GABAA receptors. The concentration-response curves for GABA are left-shifted by KRS-5Me-4-OCF3, demonstrating that KRS-5Me-4-OCF3 enhanced GABA affinity and acted as a positive allosteric modulator of GABAA receptors. The effect of KRS-5Me-4-OCF3 was blocked by applying a benzodiazepine site antagonist, suggesting that KRS-5Me-4-OCF3 binds at the classic benzodiazepine site to exert its pharmacological action. The results suggest clinical use of enaminones as anticonvulsants in seizures and as a potential anxiolytic in mental disorders.
我们对一个小型苯胺烯酮化合物库进行了分析,以寻找潜在的抗惊厥药物。我们利用全细胞贴片钳记录技术,研究了三种苯胺基烯丙酮对嗅球脑片制备中输出神经元--有丝分裂细胞(MC)的神经元活动的影响。众所周知,这些化合物能有效减轻戊四唑诱发的惊厥。在测试的三种化合物中,5-甲基-3-(4-三氟甲氧基苯基氨基)-环己-2-烯酮(KRS-5Me-4-OCF3)对 MC 活性有强效抑制作用,EC50 为 24.5 μM。它能使 MC 的膜电位超极化,同时抑制自发发射。无论是离子型谷氨酸受体阻断剂还是 GABAB 受体阻断剂,都不能阻止 KRS-5Me-4-OCF3 引发的抑制作用。在GABAA受体拮抗剂存在的情况下,KRS-5Me-4-OCF3完全不能诱发对MC尖峰活动的抑制,这表明KRS-5Me-4-OCF3诱发的抑制作用可能是通过直接作用于GABAA受体或通过提高组织GABA水平的间接作用介导的。vigabatrin(一种选择性 GABA-T 抑制剂)和 1,2,5,6-四氢-1-[2-[[(二苯基亚甲基)氨基]氧]乙基]-3-吡啶甲酸盐酸盐(NNC-711)(一种选择性抑制 GABA 转运体 1 吸收 GABA 的抑制剂)都不能消除 KRS-5ME-4-OCF3 对神经元兴奋性的影响、这表明烯氨酮的抑制作用是通过直接激活 GABAA 受体产生的。KRS-5Me-4-OCF3可使GABA的浓度-反应曲线左移,这表明KRS-5Me-4-OCF3增强了GABA的亲和力,是GABAA受体的正异位调节剂。使用苯并二氮杂卓位点拮抗剂可阻断 KRS-5Me-4-OCF3 的作用,这表明 KRS-5Me-4-OCF3 与经典的苯并二氮杂卓位点结合,从而发挥药理作用。研究结果表明,烯酰胺酮类药物可作为抗惊厥药用于临床治疗癫痫发作,也可作为潜在的抗焦虑药用于治疗精神障碍。