POSITRON EMISSION TOMOGRAPHY STUDIES ON DOPAMINE-RECEPTORS IN SCHIZOPHRENIA

The dopamine (DA) hypotheses for schizophrenia and antipsychotic drug action can be examined with greater detail using a new generation of positive emission tomography (PET) scanners and more selective radioligands. Original PET studies suggested that patients with schizophrenia might have elevated densities of DA D-2 receptors, but research conducted with more selective radioligands did not support this finding. However, we have found that D-2-receptor density may be greater in the left than in the right striatum of patients with schizophrenia. We have also found that a high occupancy of D-2 receptors in the striatum by antipsychotic drugs may correlate with the occurrence of the extrapyramidal syndrome, and we have found different occupancy patterns of D-1 and D-2 receptors for classic and atypical antipsychotic agents. Recent technologic improvements in both PET scanners and radioligand affinity will enable us to extend earlier findings and to examine the role of DA receptors in other, smaller extrastrial brain structures.