Mechanisms of action of atypical antipsychotic drugs. Implications for novel therapeutic strategies for schizophrenia.

The mechanisms which contribute to the actions of atypical antipsychotic drugs, such as clozapine and the putative atypical agents remoxipride and raclopride, are reviewed. Examination of available preclinical and clinical data leads to two hypotheses concerning the mode of action of atypical antipsychotic drugs. The first hypothesis is that antagonism of the dopamine D2 receptor is both necessary and sufficient for the atypical profile, but that interaction with subtypes of the D2 receptor differentiates typical from atypical antipsychotic drugs. The second hypothesis has been previously advanced, and suggests that a relatively high ratio of serotonin 5-HT2:dopamine D2 receptor antagonism may subserve the atypical profile. It seems likely that the atypical antipsychotic drug profile may be achieved in more than one way.