The α₁,α₂, and α₃ Subunits of GABA_A Receptors: Comparison in Seizure-Prone and -Resistant Mice and during Development

Gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in brain, opens chloride channels through actions on GABA_A receptors. We now report base and amino acid sequences of the α₁, α₂, and α₃ subunits from GABA_A receptors of audiogenic seizure-prone (DBA/2J) and -resistant (C57BL/6J) inbred strains of mice. Inbreeding had fixed different alleles of the α₁ subunit in the two strains, giving five base differences in the cDNAs. None of these affected amino acid sequence, but one did create a NsiI restriction site potentially useful in mapping genomic DNA. No base or amino acid sequence differences between the strains were detected for the other two subunits. Northern blots revealed no apparent strain differences in message levels for these three subunits in whole brains of the mice at 3 weeks of age, the peak of seizure susceptibility in DBA/2J, but did reveal distinct regional and developmental patterns of expression among the subunits in mouse brain.