Autoradiographic demonstration of the selectivity of two 1-N-trifluoroethyl benzodiazepines for the BZD-1 receptors in the rat brain.

Receptor autoradiographic techniques have been used to demonstrate the selectivity of two trifluoroethyl-containing benzodiazepines for one of the subtypes of benzodiazepine receptor. Indirect localization of the binding sites for quazepam and halazepam was accomplished by using the ability of these compounds to displace [3H]-flunitrazepam binding. The appropriate binding parameters were selected on the basis of initial studies aimed at identifying the binding characteristics of several benzodiazepine compounds in comparison with the triazolopyridine CL218,872. Autoradiographic analysis of the benzodiazepine sites displaceable with quazepam and halazepam revealed the two benzodiazepine compounds preferentially labeled receptor sites in regions of the brain dominated by the type 1 benzodiazepine receptor subtype. Thus, quazepam and halazepam preferentially bind to benzodiazepine type-1 receptors in lamina IV of the cerebral cortex, the zona incerta, substantia nigra and the cerebellum.