Raymond V, Mongan N P, Sattelle D B
MRC Functional Genetics Unit, Department of Human Anatomy and Genetics, University of Oxford, South Parks Road, OX1 3QX, Oxford, UK.
Neuroscience. 2000;101(3):785-91. doi: 10.1016/s0306-4522(00)00279-7.
Two homomer-forming nicotinic acetylcholine receptor subunits with 47% identity in their amino acid sequences were employed to compare the actions of cholinergic anthelmintics and ivermectin on expressed vertebrate and nematode nicotinic receptors of known molecular composition. Voltage-clamp electrophysiology was used to study recombinant nicotinic receptors expressed in Xenopus laevis oocytes following nuclear injection of cDNA encoding either chicken alpha7 or Caenorhabditis elegans ACR-16 (Ce21) subunits. Butamisole, morantel and metyridine were without agonist actions on either alpha7 or ACR-16 nicotinic receptors in the range 10nM-1mM. However, butamisole (pIC(50)=4.9 for both alpha7 and ACR-16) and morantel (pIC(50)=5.6 for alpha7 and 5.7 for ACR-16) antagonized responses of both alpha7 and ACR-16 receptors to acetylcholine. Metyridine (1mM) did not affect responses to acetylcholine of either receptor. Oxantel was without agonist actions on ACR-16, but was an acetylcholine antagonist (pIC(50)=5.4). In contrast, it was found to have low efficacy agonist action (pEC(50)=4.4) on alpha7 at concentrations in the range 10-300microM. In agreement with a previous study, ivermectin (30microM), an agonist of L-glutamate-gated chloride channels, enhanced the amplitude of responses to acetylcholine of alpha7 nicotinic receptors. However, this same concentration of ivermectin (30microM) did not potentiate the acetylcholine-induced responses of ACR-16, but rather resulted in a slight attenuation. We conclude that oxantel and ivermectin have identified new pharmacological differences between the chicken alpha7 nicotinic receptor and its C. elegans homologue ACR-16.
使用了两个在氨基酸序列上具有47%同一性的同聚体形成型烟碱型乙酰胆碱受体亚基，以比较胆碱能驱虫药和伊维菌素对已知分子组成的表达型脊椎动物和线虫烟碱型受体的作用。采用电压钳电生理学方法，研究在非洲爪蟾卵母细胞中表达的重组烟碱型受体，这些受体是通过核注射编码鸡α7或秀丽隐杆线虫ACR-16（Ce21）亚基的cDNA后获得的。丁咪酰胺、噻嘧啶和甲噻嘧啶在10 nM至1 mM范围内对α7或ACR-16烟碱型受体均无激动剂作用。然而，丁咪酰胺（α7和ACR-16的pIC(50)均为4.9）和噻嘧啶（α7的pIC(50)为5.6，ACR-16的pIC(50)为5.7）拮抗α7和ACR-16受体对乙酰胆碱的反应。甲噻嘧啶（1 mM）对两种受体对乙酰胆碱的反应均无影响。奥克太尔对ACR-16无激动剂作用，但它是一种乙酰胆碱拮抗剂（pIC(50)=5.4）。相比之下，发现在10至300 μM浓度范围内，它对α7具有低效激动剂作用（pEC(50)=4.4）。与先前的一项研究一致，L-谷氨酸门控氯离子通道激动剂伊维菌素（30 μM）增强了α7烟碱型受体对乙酰胆碱的反应幅度。然而，相同浓度的伊维菌素（30 μM）并未增强ACR-16对乙酰胆碱的诱导反应，反而导致轻微减弱。我们得出结论，奥克太尔和伊维菌素揭示了鸡α7烟碱型受体与其秀丽隐杆线虫同源物ACR-16之间新的药理学差异。
