Trichloroethanol modulation of recombinant GABAA, glycine and GABA rho 1 receptors.
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.
Krasowski
M D
MD
Department of Anesthesia and Critical Care, University of Chicago, Illinois, USA. kra3@harper.uchicago.edu
Finn
S E
SE
Ye
Q
Q
Harrison
N L
NL
D000595:Amino Acid Sequence; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005023:Ethylene Chlorohydrin / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018079:Receptors, GABA / Q000187:drug effects*; D011963:Receptors, GABA-A / Q000187:drug effects*; D018009:Receptors, Glycine / Q000187:drug effects*; D013329:Structure-Activity Relationship
C087200:GABA-C receptor; D018079:Receptors, GABA; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; D005023:Ethylene Chlorohydrin; C005849:2,2,2-trichloroethanol