Good Correlations between Brain Levels of Benzodiazepines determined by Radioreceptorassay and Central Nervous System Activity

A radioreceptorassay with 3H-diazepam and benzodiazepine receptors was used to determine the levels of receptor reactive substances (diazepam activity) in various brain regions after i.p. injection of six benzodiazepines (2 mg/kg) into rats. All the compounds tested gave nearly the same regional distribution. The correlations between diazepam activities and pharmacological or clinical potencies were better than those between in vitro binding data and central nervous system activities. This result indicates that the determination of diazepam activity in the brain by the radioreceptorassay technique is useful for evaluating the pharmacological and clinical potencies of benzodiazepines and related compounds.