Localization of diazepam-binding inhibitor (DBI) mRNA in the rat brain by high resolution in situ hybridization.

An endogenous peptide, named diazepam-binding inhibitor (DBI) capable of displacing benzodiazepines from binding sites has been recently fully characterized. In order to clearly identify the cell types responsible for the biosynthesis of DBI in the rat central nervous system, we have performed high resolution in situ hybridization in the area postrema, hypothalamus and cerebellum, using a [35S]-labeled single stranded RNA probe. Hybridization signal was detected in both semithin and ultrathin sections. In all the brain areas examined, specific labeling was exclusively observed in non-neuronal cells including ependymal and subependymal cells bordering the third ventricle. The results obtained clearly establish that DBI is synthesized by non-neuronal cells in the rat brain.