RAT PITUITARY-CELLS SELECTIVELY EXPRESS MESSENGER-RNA ENCODING THE SHORT ISOFORM OF THE GAMMA-2GABAA 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 alpha, beta, gamma and delta contain multiple variants. We have measured the steady-state levels of mRNAs encoding different (alpha-1, alpha-4, beta-1, beta-2, beta-3, gamma-2 long, gamma-2 short and delta) 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 alpha-1, beta-1 and beta-3 GABA(A) receptor subunits whereas the transcripts for alpha-4, beta-2 and delta were undetectable. We also found that pituitary cells selectively express the short isoform of the gamma-2 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.