Poly(A)^+mRNA翻译产生的GABA受体-氯离子通道复合体

GABA receptor-chloride channel complex produced by poly (A)^+mRNA translation

采用生化药理学方法首次在注射了胚鸡脑poly(A)^+mRNA的非洲爪蟾卵母细胞表面检测到GABA受体复合体,从生化角度证实了移植GABA受体、安定受体的结合部位及其功能部位氯离子通道的存在。注射Barth液和poly(A)RNA的卵母细胞不能表达此受体复合体。放射性配体结合实验中,〔~3H〕FNZP终浓度高于0.6nmol/L时,结合趋于饱和,K_D=1.17nmol/L,B_(max)=1.5fmol/cell。此结合可被过量的氟安定抑制,而不受QNB的影响。蝇蕈醇(20μmol/L),内源性GABA受体激动剂(19μg/μl),苯巴比妥(500μmol/L)可以增强移植安定受体与〔~3H〕FNZP的结合。GABA(2μmol/L)及低浓度的印防己毒素(50μmol/L)对结合无影响,较高浓度(125μmol/L)的印防己毒素对结合有抑制作用。

GABA receptor-chloride channel complex was identified for the first time with a biochemical pharmacological method on the surface of Xenopus laevis oocytes previously injected with chick embryo brain poly(A)+mRNA.The oocytes injected with poly(A)-RNA failed to translate the complex.The radioligand-receptor binding assay showed that the binding of [3H] FNZP to translated benzo-diazepine receptors was saturable and specific(KD= 1.17nmol/L,Bmax=1.5fmol/cell).The binding was saturated at 0.6 nmol/L and could be completely inhibited by flurodiazepam but was not affected by muscarinic receptor ligand QNB.The binding was clearly enhanced by the GABA receptor ligands muscimol(20μmol/L)and the GABA receptor agonist(a new endogenous GABA receptor ligand isolated in our laboratory)or by pentobarbital(500μmmol/L).Picrotoxin did not af-fect the binding at 50μmol/L but inhibited it at 125 μmol/L.