Independent cellular and ontogenetic expression of mRNAS encoding three α polypeptides of the rat GABAA receptor

Previous studies have shown that several distinct but related polypeptides can serve as α subunits of functional GABA A receptors. Furthermore, the diversity of these polypeptides at least partially accounts for the functional heterogeneity of GABA A receptors. In this paper, we report the results of in situ hybridization studies using probes derived from our recently reported cDNAs for α 1 , α 2 , and α 4 GABA A receptor polypeptides. We show that the mRNAs that encode these isoforms have distinct regional and cellular distributions and are present at widely varying levels within the rat brain. In addition, our Northern blot analyses indicate that each of these three α mRNAs has a distinct pattern of ontogenetic regulation. Differential regulation of a polypeptide isoforms may lead to changes in GABA A receptor function during ontogeny as well as to distinct cellular responses to GABA and GABA-related drugs.