Risperidone: a novel antipsychotic with many "atypical" properties?

The acute and chronic administration effects of risperidone (Ris), a mixed 5HT2/D2 receptor antagonist, versus haloperidol (Hal) on dopaminergic and serotoninergic activity were investigated in the rat prefrontal cortex (Pfc), and the whole striatum (Str) as well as separately, in dorsal striatum (StrD) and nucleus accumbens (Acb). During acute administration, Hal was found to be more potent than Ris in increasing DA turnover rate in StrD. In contrast, during chronic administration, Ris but not Hal, continued to increase DA turnover activity in StrD. Moreover, in contrast to Hal, chronic Ris treatment continued to increase DA and 5-HT turnover rate in Pfc. These differential effects reveal that Hal does not share common characteristics with Ris with respect to its neurochemical profile in the Str and Pfc.