A study of benzodiazepine receptor in human brain using 11C-Ro 15-1788 and positron emission tomography

A study of benzodiazepine receptor was performed in 15 healthy normal volunteers using carbon-11 labeled Ro 15-1788 and positron emission tomography. The brain kinetics of 11C-Ro 15-1788 showed a high uptake of the tracer by the brain, the maximum of which was within 20 minutes. The early distribution of the tracer after injection showed a regional distribution similar to that of any perfusion tracer with high activity in the cerebral cortex, the basal ganglia, the thalamus and the cerebellum. The peak of the radioactivity was reached earlier in the basal ganglia, the thalamus and the cerebellum than in the cerebral cortex. The accumulation of 11C was highest in the cerebral cortex, moderate in the thalamus, the basal ganglia and the cerebellum and low in the brain stem at 20 minutes post-injection. The distribution of the tracer at 20 minutes post-injection was approximately parallel to the known distribution of benzodiazepine receptors (Bsub(max)) in human in vitro. Cold Ro 15-1788 was administered with the dose of 0.3 mg/kg, 0.5 mg/kg and 1.1 mg/kg in three volunteers 30 minutes prior to injection. The radioactivity in the cerebral cortex were reduced to 48 %, 22 %, and 31 % of those in the control experiments respectively. About half of the injected tracer was excreted in the urine at 1 hour after injection. 11C-Ro 15-1788 is a potent radioligand to study benzodiazepine receptors in vivo in human. (author)