Expression of brain mRNA or cRNAs in Xenopus oocytes was used to determine what subunits of the GABAA 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 β1, β1, γ1, γ2S+2L, γ2L, or γ3 subunits did not alter GABA action or enhancement by pentobarbital. Action of diazepam was prevented by antisense oligonucleotides to γ2S+2L and reduced by antisense sequences to γ2L, but was not affected by the other oligonucleotides. Ethanol enhancement of GABA action was prevented only by antisense oligonucleotides to γ2L (which differs from γ2S by the addition of 8 amino acids). Expression of either the α1β1γ2S or the α1β1γ2L subunit cRNA combination in oocytes resulted in GABA responses that were enhanced by diazepam or pentobarbital, but only the combination containing the γ2L subunit was affected by ethanol.
Bibliographical noteFunding Information:
We thank Dr. Bill Proctor for assistance with the electrophysiological techniques and Donna Wilson-Shaw and Misi Robinson for excellent technical assistance. This research was supported by grants AAO6399, AA03527, AAO7559, and NS27322 and the Veterans Administration.