IBZM-SPECT IMAGING OF DOPAMINE D-2 RECEPTORS WITH TYPICAL AND ATYPICAL ANTIPSYCHOTICS

Considerable progress has been achieved over the past 15 years in unco vering the biological basis of major psychiatric disorders. Since psyc hopharmacological treatment is thought to act on the underlying biolog ical basis of the disease, brain imaging techniques enable us to under stand the mechanism of action of such compounds. One important tool us ed to determine patterns of brain dysfunction and how psychopharmacolo gical agents such as antipsychotic compounds work is single-photon emi ssion computerised tomography (SPECT). This technique allows determina tion of striatal D-2 receptor occupancy rates, which are associated wi th the extrapyramidal side effects (EPS) of antipsychotic drugs. Studi es have confirmed that atypical antipsychotic agents have lower occupa ncy rates than typical agents. No association has been found between D -2 receptor occupancy rates in the striatum and antipsychotic efficacy , and it therefore appears that striatal D-2 receptor occupancy rates are not necessary for the antipsychotic effect of such agents in schiz ophrenia. The availability of more refined radioligands will help us n ot only to understand the action of antipsychotics but also the pathop hysiology of schizophrenia.