Clinical implications of dopamine research in schizophrenia

One of the most stimulating problems posed by second generation antipsychotics is the question of whether their ability to act on the negative, as well as the positive, symptoms of schizophrenia relies on the same neurochemical mechanisms as those responsible for their lack of extrapyramidal symptoms (EPS). Amisulpride is a substituted benzamide antipsychotic, which is known to be efficacious against both the positive and the negative symptoms of schizophrenia and to have a lower propensity to induce EPS than conventional antipsychotics. Amisulpride preferentially blocks the D2 and D3 subtypes of dopamine receptors, both presynaptically in the frontal cortex, enhancing dopaminergic transmission, and postsynaptically in subcortical areas such as the nucleus accumbens, so reducing dopaminergic transmission. Given that dopaminergic under-activity in the frontal cortex is thought to produce negative symptoms, and over-activity in the limbic system to produce positive symptoms, it is proposed that these are the mechanisms by which amisulpride produces its atypical profile.