Detection and determination of pharmacologically active benzodiazepines in rat brain after the administration of 2-o-chlorobenzoyl-4-chloro-N-methyl-N'-glycylglycinanilide, using a combination of high-pressure liquid chromatography and radioreceptorassay.

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In the present work we attempted to detect and quantitate central nervous system (CNS)-active benzodiazepines in rat brain after administration of a peptido-aminobenzophenone. The results can be summarized as follows. 1. Radioreceptorassay (RRA) using 3H-diazepam as the labeled ligand and ratbrain crude synaptosomes was a simple, reliable and sensitive assay method for benzodiazepines. 2. A benzene extract of a rat brain homogenate prepared 15 min after i.p. administration of 2-o-chlorobenzoyl-4-chloro-N-methyl-N'-glycylglycinanilide (1) was subjected to high pressure liquid chromatography (HPLC). By RRA analysis of the eluted fractions, four benzodiazepines having high affinity for benzodiazepine receptors were detected. 3. Changes in the levels of each benzodiazepine in rat brains after i.p. administration of 1 were determined by a combination of HPLC and RRA. The levels can account for the CNS activities of 1. 1 itself could not be detected throughout the experiments. These results strongly indicate that 1 exerts its CNS activities through conversion into CNS-active benzodiazepines in vivo.