RISPERIDONE - A NOVEL ANTIPSYCHOTIC WITH MANY ATYPICAL PROPERTIES

The acute and chronic administration effects of risperidone (Ris), a m ixed 5HT(2)/D-2 receptor antagonist, versus haloperidol (Hal) on dopam inergic and serotoninergic activity were investigated in the rat prefr ontal 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 incre ase DA and 5-HT turnover rate in Pfc. These differential effects revea l that Hal does not share common characteristics with Ris with respect to its neurochemical profile in the Str and Pfc.