Neurogenic actions of atypical antipsychotic drugs and therapeutic implications.

Brain imaging and postmortem studies have reported a reduction in the volume of discrete brain regions, as well as cellular abnormalities in schizophrenic patients. In addition, basic research studies have demonstrated effects of antipsychotic drugs on cell morphology and number. Of particular interest is adult neurogenesis, which has been linked to cognitive and memory improvements, and is also associated with the behavioural actions of antidepressants. While the action of antidepressant treatment is restricted mainly to the hippocampus, long-term administration of antipsychotics is reported to increase neurogenesis in the subventricular zone (SVZ), as well as the subgranular zone (SGZ) of the hippocampus. In addition, antipsychotic drugs increase the proliferation of non-neuronal cell types in the prefrontal cortex and could thereby influence the function of this brain region. Typical and atypical antipsychotic drugs differentially regulate neurogenesis in the SVZ and SGZ. Although the therapeutic relevance remains speculative, the results are consistent with the hypothesis that the actions of antipsychotic agents could be mediated, in part, by increased proliferation of neuronal as well as glial cells. Additional animal studies and postmortem analyses are required to further test this possibility and to investigate the relevance of this work in the pathophysiology and treatment of schizophrenia.