Use of the selective benzodiazepine-1 (BZ-1) ligand [3H]2-oxo-quazepam (SCH 15-725) to localize BZ-1 receptors in the rat brain.

Receptor autoradiographic techniques have been used to localize benzodiazepine-1 (BZ-1) receptor sites by employing a tritiated form of 2-oxo-quazepam (SCH 15-725), a metabolite of the benzodiazepine quazepam (SCH 16-134). Labeling of the receptors was quantitatively determined to be most abundant in areas of the rat brain known through previous autoradiographic studies to bind preferentially with BZ-1 selective ligands. These areas include lamina IV of the parietal cortex, substantia innominata, anterior amygdaloid nucleus, substantia nigra, zona incerta, and molecular layer of the cerebellum. Autoradiographic localization of binding sites for [3H]2-oxo-quazepam provides additional support for the hypothesis that this compound identifies the BZ-1 receptor subtype and demonstrates the utility of this ligand for quantitation of the distribution and density of these sites.