Krasowski M D, Finn S E, Ye Q, Harrison N L
Department of Anesthesia and Critical Care, University of Chicago, Illinois, USA.
J Pharmacol Exp Ther. 1998 Mar;284(3):934-42.
The actions of 2,2,2,-trichloroethanol were studied on agonist-activated Cl- currents in gamma-aminobutyric acid type A (GABAA), glycine and GABA rho 1 receptors by use of the whole-cell patch-clamp technique. Recombinant wild-type and mutant receptor subunits were transiently expressed in human embryonic kidney (HEK) 293 cells. Trichloroethanol enhanced currents elicited by submaximal (EC20) agonist concentrations at GABAA alpha 2 beta 1 receptors and glycine alpha 1 homomeric receptors in a reversible, concentration-dependent manner. Trichloroethanol, at concentrations of < or = 2 mM, did not significantly alter the magnitude of submaximal GABA currents at GABA rho 1 receptors, whereas higher concentrations inhibited submaximal GABA currents. Recent work has identified residues within putative transmembrane domains 2 and 3 as critical for positive modulation of GABAA and glycine receptors by n-alkanols and volatile ether anesthetics. Submaximal glycine currents at receptors containing either of two specific mutations within the glycine receptor alpha 1 subunit (S267I and A288W) were not enhanced by low concentrations of trichloroethanol and were inhibited by higher concentrations of trichloroethanol. In the GABAA alpha 2 beta 1 receptor, a specific mutation within transmembrane domain 3 of the beta 1 subunit (M286W) also abolished positive modulation by trichloroethanol. Mutations within the GABAA alpha 2 receptor subunit did not alter positive modulation by TCEt, whereas such mutations ablate positive modulation by n-alkanols and volatile anesthetics. In summary, trichloroethanol modulation of GABAA, glycine and GABA rho 1 receptors shares some, but not all, features in common with the requirements for modulation by n-alkanols and volatile anesthetics.
采用全细胞膜片钳技术，研究了2,2,2-三氯乙醇对γ-氨基丁酸A型（GABAA）、甘氨酸和GABA rho 1受体激动剂激活的氯离子电流的作用。重组野生型和突变型受体亚基在人胚肾（HEK）293细胞中瞬时表达。三氯乙醇以可逆的、浓度依赖性方式增强了在GABAA α2β1受体和甘氨酸α1同聚体受体上由次最大（EC20）激动剂浓度引发的电流。浓度≤2 mM的三氯乙醇不会显著改变GABA rho 1受体上次最大GABA电流的大小，而较高浓度则会抑制次最大GABA电流。最近的研究已确定，假定的跨膜结构域2和3内的残基对于正烷醇和挥发性醚类麻醉剂对GABAA和甘氨酸受体的正向调节至关重要。甘氨酸受体α1亚基内两个特定突变（S267I和A-288W）之一的受体上的次最大甘氨酸电流，不会被低浓度的三氯乙醇增强，反而会被高浓度的三氯乙醇抑制。在GABAA α2β1受体中，β1亚基跨膜结构域3内的一个特定突变（M286W）也消除了三氯乙醇的正向调节作用。GABAA α2受体亚基内的突变不会改变三氯乙醇的正向调节作用，而此类突变会消除正烷醇和挥发性麻醉剂的正向调节作用。总之，三氯乙醇对GABAA、甘氨酸和GABA rho 1受体的调节与正烷醇和挥发性麻醉剂调节的要求有一些但并非全部共同特征。
