Rat pituitary cells selectively express mRNA encoding the short isoform of the γ2 GABAA receptor subunit

The GABA_A receptor belongs to the ligand-gated ion channel receptor superfamily and appears to be composed of from 4 to 5 subunits which interact with each other. Molecular cloning of cDNAs encoding the different subunits of the GABA_A receptor has revealed an unexpected heterogeneity which includes at least 4 homologous classes of subunits: these classes, designated as α, β, γ and δ contain multiple variants. We have measured the steady-state levels of mRNAs encoding different (α1, α4, β1, β2, β3, γ2 long, γ2 short and δ) GABA_A receptor subunits in the rat anterior pituitary and cerebellum using a polymerase chain reaction (PCR)-derived method. We found that pituitary cells express mRNAs encoding the α1, β1 and β3 GABA_A receptor subunits whereas the transcripts for α4, β2 and δ were undetectable. We also found that pituitary cells selectively express the short isoform of the γ2 subunit mRNA. These data indicate that the expression of the various GABA_A receptor subunits is cell-specific and support the concept that the diversity in function and pharmacology of the GABA_A receptor is based on the ability of cells to specify the expression of selective GABA_A receptor subunits.