TRICHLOROETHANOL MODULATION OF RECOMBINANT GABA(A), GLYCINE AND GABA RHO(1) RECEPTORS

The actions of 2,2,2,-trichloroethanol were studied on agonist-activat ed Cl- currents in gamma-aminobutyric acid type A (GABA(A)), glycine a nd GABA rho(1) receptors by use of the whole-cell patch-clamp techniqu e. 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 concentration s at GABA(A) alpha(2) beta(1) receptors and glycine alpha(1) homomeric receptors in a reversible, concentration-dependent manner. Trichloroe thanol, at concentrations of less than or equal to 2 mM, did not signi ficantly alter the magnitude of submaximal GABA currents at GABA rho(1 ) receptors, whereas higher concentrations inhibited submaximal GABA c urrents. Recent work has identified residues within putative transmemb rane domains 2 and 3 as critical for positive modulation of GABA(A) an d glycine receptors by n-alkanols and volatile ether anesthetics. Subm aximal glycine currents at receptors containing either of two specific mutations within the glycine receptor alpha(1) subunit (S-267\ and A( 288)W) were not enhanced by low concentrations of trichloroethanol and were inhibited by higher concentrations of trichloroethanol, in the G ABA(A) alpha(2) beta(1) receptor, a specific mutation within transmemb rane domain 3 of the beta(1) subunit ((MW)-W-286) also abolished posit ive modulation by trichloroethanol. Mutations within the GABA(A) alpha (2) receptor subunit did not alter positive modulation by TCEt, wherea s such mutations ablate positive modulation by n-alkanols and volatile anesthetics. In summary, trichloroethanol modulation of GABA(A), glyc ine and GABA rho(1) receptors shares some, but not all, features in co mmon with the requirements for modulation by n-alkanols and volatile a nesthetics.