STRIATAL AND EXTRASTRIATAL IMAGING OF DOPAMINE D-2 RECEPTORS IN THE LIVING HUMAN BRAIN WITH [I-123] EPIDEPRIDE SINGLE-PHOTON EMISSION TOMOGRAPHY

The iodine-123 labelled ligand benzamide epidepride was evaluated as a probe for in vivo imaging of striatal and extrastriatal dopamine D-2 receptor sites in the human brain. Four healthy males were imaged with a high-resolution single-photon emission tomography scanner. Striatal radioactivity peaked at 3 h after injection. The specific binding in the striatum was 0.91+/-0.03 at 3 h and this ratio steadily increased with time. Extrastriatal radioactivity was highest in the thalamus, in the midbrain and in the temporal cortex, and peaked at 45-60 min afte r injection of tracer. A smaller amount of radioactivity was found in the parietal, frontal and occipital cortices. Two radioactive metaboli tes were observed, of which one was more lipophilic than the parent co mpound. The radiation burden to the patient was 0.035 mSv/MBq (effecti ve dose equivalent). The preliminary results showed that [I-123]epidep ride can be used for imaging striatal and extrastriatal dopamine D-2 r eceptor sites in the living human brain.