PET IMAGING OF NEURORECEPTORS IN SCHIZOPHRENIA

Among the brain imaging techniques developed during the past two decad es positron emission tomography has the highest sensitivity, allowing the analysis of specific neurotransmitter mechanisms in the living hum an brain. By using a combination of selective ligands labelled with po sitron emitting isotopes, D-1 and D-2 dopamine, serotonin 5HT(2) and b enzodiazepine receptors were examined in schizophrenic patients (DSM-I IIR) and healthy control subjects. With this technique receptor popula tions could be excellently visualized and quantified with regard to nu mber and binding characteristics in several brain regions. The charact eristics of total D-1 and D-2 dopamine receptor populations in the cau date and putamen did not differ significantly in young drug naive schi zophrenic patients and age matched control subjects. On the other hand , there was a highly significant reduction of the D-1 signal in high i ntensity regions of the basal ganglia when [C-11]SCH 23390, a selectiv e D-1 dopamine receptor antagonist, was used. These results suggest th e possibility of a reduced D-1 dopamine receptor density in the patch compartment of the basal ganglia in schizophrenia. For 5HT(2) and benz odiazepine receptors no major alteration of receptor characteristics w as observed in several neocortical and limbic brain regions.