Neelands T R, Greenfield L J, Zhang J, Turner R S, Macdonald R L
Neuroscience Program, University of Michigan, Ann Arbor, Michigan 48104-1687, USA.
J Neurosci. 1998 Jul 1;18(13):4993-5007. doi: 10.1523/JNEUROSCI.18-13-04993.1998.
Human NT2 teratocarcinoma cells differentiate into neuron-like NT2-N cells when treated with retinoic acid. GABA evoked concentration-dependent whole-cell currents in NT2-N cells with an EC50 of 21.8 microM and a Hill slope of 1.2. GABAA receptor (GABAR) currents reversed at ECl- and did not display voltage-dependent rectification. GABAR single channels opened in bursts to a 23 pS main conductance level and a 19 pS subconductance level, with infrequent openings to a 27 pS conductance level. Kinetic properties of the main conductance level were similar to other native and recombinant GABAR channels. Diazepam and zolpidem enhanced GABAR currents with moderate affinity, whereas methyl-6, 7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate inhibited GABAR currents. Loreclezole enhanced GABAR currents with high affinity, but furosemide antagonized GABAR currents with low affinity. The neurosteroids alphaxalone and pregnenolone sulfate appropriately modulated GABAR currents. Zinc blocked GABAR currents with low affinity, but lanthanum did not significantly alter NT2-N GABAR currents. Reverse transcription PCR (RT-PCR) performed on RNA from NT2-N cells clearly detected transcripts encoding human alpha2, alpha3, alpha5, beta3, gamma3, and pi subtypes. The combined pharmacological and RT-PCR results are most consistent with a single or predominant GABAR isoform composed of an alpha2 and/or alpha3 subtype combined with the beta3 and gamma3 subtypes. The data do not rule out receptors containing combinations of alpha2 and/or alpha3 subtypes with the alpha5 subtype or receptors with both beta1 and beta3 subtypes. The presence or absence or the pi subunit in functionally expressed receptors could not be determined.
人NT2畸胎瘤细胞在用视黄酸处理后可分化为神经元样NT2 - N细胞。γ-氨基丁酸（GABA）在NT2 - N细胞中诱发浓度依赖性全细胞电流，其半数有效浓度（EC50）为21.8微摩尔，希尔系数为1.2。GABAA受体（GABAR）电流在氯离子平衡电位（ECl-）处反转，且不表现出电压依赖性整流。GABAR单通道以突发形式开放至23皮西门子（pS）的主电导水平和19 pS的次电导水平，偶尔开放至27 pS电导水平。主电导水平的动力学特性与其他天然和重组GABAR通道相似。地西泮和唑吡坦以中等亲和力增强GABAR电流，而甲基-6,7 - 二甲氧基-4 - 乙基-β-咔啉-3 - 羧酸酯抑制GABAR电流。氯雷唑以高亲和力增强GABAR电流，但呋塞米以低亲和力拮抗GABAR电流。神经甾体类药物阿法沙龙和硫酸孕烯醇酮可适当调节GABAR电流。锌以低亲和力阻断GABAR电流，但镧对NT2 - N细胞的GABAR电流无显著影响。对NT2 - N细胞RNA进行的逆转录聚合酶链反应（RT - PCR）清楚地检测到编码人α2、α3、α5、β3、γ3和π亚型的转录本。药理学和RT - PCR结果相结合，最符合由α2和/或α3亚型与β3和γ3亚型组成的单一或主要GABAR亚型。数据不排除含有α2和/或α3亚型与α5亚型组合的受体，或同时含有β1和β3亚型的受体。在功能表达的受体中，无法确定π亚基的存在与否。
