Division of Pharmacology and Toxicology, Waggoner Center for Alcohol & Addiction Research, Institutes for Neuroscience and Cell & Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
Neuropharmacology. 2012 Sep;63(3):368-73. doi: 10.1016/j.neuropharm.2012.04.011. Epub 2012 Apr 24.
Trifluoroacetic acid is a metabolite of the inhaled anesthetics halothane, desflurane and isoflurane as well as a major contaminant in HPLC-purified peptides. Ligand-gated ion channels, including cys-loop receptors such as the glycine receptor, have been the targets of peptide-based drug design and are considered to be likely candidates for mediating the effects of anesthetics in vivo, but the possible secondary contributions of contaminants and metabolites to these effects have not been studied. We used two-electrode voltage-clamp electrophysiology to test glycine, GABA(A) and 5-HT3 receptors expressed in Xenopus oocytes for their sensitivities to sodium trifluoroacetate. Trifluoroacetate (100 μM-3mM) enhanced the currents elicited by low concentrations of glycine applied to α1 homomeric and α1β heteromeric glycine receptors, but it had no effects when co-applied with a maximally-effective glycine concentration. Trifluoroacetate had no effects on α1β2γ2S GABA(A) or 5-HT3A receptors at any GABA or serotonin concentration tested. The results demonstrate that trifluoroacetate acts as an allosteric modulator at the glycine receptor with greater specificity than other known modulators. These results have important implications for both the secondary effects of volatile anesthetics and the presence of contaminating trifluoroacetate in HPLC-purified peptides, which is potentially an important source of experimental variability or error that requires control.
三氟乙酸是吸入麻醉剂氟烷、七氟醚和异氟醚的代谢物，也是 HPLC 纯化肽中的主要污染物。配体门控离子通道，包括 cys-环受体，如甘氨酸受体，一直是基于肽的药物设计的靶点，被认为是体内麻醉剂作用的可能候选介质，但污染物和代谢物对这些作用的可能次要贡献尚未得到研究。我们使用双电极电压钳电生理学方法，测试了 Xenopus oocytes 中表达的甘氨酸、GABA(A)和 5-HT3 受体对三氟乙酸钠的敏感性。三氟乙酸（100 μM-3mM）增强了低浓度甘氨酸对 α1 同源和 α1β 异源甘氨酸受体引发的电流，但在与最大有效甘氨酸浓度共同应用时没有效果。三氟乙酸在任何 GABA 或 5-HT 浓度下对 α1β2γ2S GABA(A)或 5-HT3A 受体均无影响。结果表明，三氟乙酸作为甘氨酸受体的变构调节剂发挥作用，其特异性高于其他已知调节剂。这些结果对挥发性麻醉剂的次要作用以及 HPLC 纯化肽中存在污染的三氟乙酸具有重要意义，这可能是实验变异性或误差的重要来源，需要加以控制。
