Antibodies directed against a nonapeptide sequence of the γ-aminobutyrate (GABA)/benzodiazepine receptor α-subunit. Detection of a distinct α-like subunit in pig cerebral cortex but not cerebellum

A synthetic peptide, corresponding to amino acid residues 101-109 of the bovine gamma-aminobutyrate/benzodiazepine receptor alpha-subunit, was used to raise a polyclonal antiserum. The reactivity of this antiserum towards polypeptides of both bovine and pig receptor preparations was established by immunoprecipitation and immunoblotting. Anti-peptide antibodies recognized the alpha-subunit (51 kDa) of receptor prepared from pig cerebellum or cerebral cortex. However, a polypeptide of 57 kDa was additionally recognized in cortical, but not cerebellar, preparations. This alpha-like polypeptide appeared larger than the band of polypeptides labelled irreversibly with [3H]muscimol (beta-subunit, 55-57 kDa) and corresponds to a polypeptide detected only in cortex after silver-staining or irreversible labelling with [3H]flunitrazepam. These results support the idea that the distinct regional patterns of polypeptides labelled irreversibly with [3H]flunitrazepam reflect the existence of heterologous distributions of distinct alpha-like subunits.