Regional specificity of benzodiazepine receptor down-regulation during chronic treatment of rats with flurazepam.

[3H]Flunitrazepam binding was studied in synaptosomal membranes from rat brain following 4 weeks of chronic treatment with 100-150 mg/kg/day flurazepam. At 12 h after the end of treatment, the brain was removed and dissected into 8 areas: cerebral cortex, hippocampus, cerebellum, corpus striatum, hypothalamus, midbrain-thalamus, medulla-pons, and olfactory bulbs. Membranes from each area were extensively 'washed', and saturation binding studies performed. Chronic flurazepam treatment caused a reduction in the apparent number of binding sites (Bmax) that was confined to the cerebral cortex, hippocampus, and medulla-pons, with a possible smaller loss in the olfactory bulbs. The binding constant (KD) was unchanged in all areas studied.