Pharmacological characterization and region‐specific expression in brain of the β2‐ and β3‐subunits of the rat GABAA receptor

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Abstract
The cDNA for a third β‐subunit of the rat GABAa receptor has been cloned using another β‐subunit, which we had previously cloned [(1989) FEBS Lett. 246, 145‐148], as a probe. The ~ 8‐kb cDNA for this β‐subunit (termed β2) encodes a protein of 474 amino acid residues that shares ~ 80% sequence identity with the rat and bovine β1‐ and β3‐subunits. Coexpression of the cloned β‐subunit cDNA with the α1‐subunit cDNA of the rat GABAa receptor in Xenopus oocytes produced a functional receptor and Cl− channel with pharmacological characteristics of a GABAa receptor. In contrast to interchanging α‐subunits [(1988) Nature 335, 76‐79], exchange of β2‐ or β3‐subunits in α1/β receptor complex did not markedly alter the pharmacological properties of expressed receptors. In situ hybridization histochemistry with synthetic subunit‐specific oligodeoxynucleotide probes revealed a region‐specific expression of α1‐, β2‐ and β3‐subunit mRNAs in the rat central nervous system. These observations provide an additional molecular basis for the functional heterogeneity in the GABAA receptor complex.