ETHANOL SENSITIVITY OF THE GABA-A RECEPTOR EXPRESSED IN XENOPUS OOCYTES REQUIRES 8 AMINO-ACIDS CONTAINED IN THE GAMMA-2L SUBUNIT

Expression of brain mRNA or cRNAs in Xenopus oocytes was used to determine what subunits of the GABA(A) receptor are required for modulation by barbiturates, benzodiazepines, and ethanol. Mouse brain mRNA was hybridized with antisense oligonucleotides complementary to sequences unique to specific subunits and injected into oocytes. Antisense oligonucleotides to the alpha-1, beta-1, gamma-1, gamma-2S + 2L, gamma-2L, or gamma-3 subunits did not alter GABA action or enhancement by pentobarbital. Action of diazepam was prevented by antisense oligonucleotides to gamma-2S + 2L and reduced by antisense sequences to gamma-2L, but was not affected by the other oligonucleotides. Ethanol enhancement of GABA action was prevented only by antisense oligonucleotides to gamma-2L (which differs from gamma-2S by the addition of 8 amino acids). Expression of either the alpha-1-beta-1-gamma-2S or the alpha-1-beta-1-gamma-2L subunit cRNA combination in oocytes resulted in GABA responses that were enhanced by diazepam or pentobarbital, but only the combination containing the gamma-2L subunit was affected by ethanol.