HALOPERIDOL AND FLUPHENAZINE INDUCE JUNB GENE-EXPRESSION IN RAT STRIATUM AND NUCLEUS-ACCUMBENS

Administration of neuroleptics such as haloperidol to rats is known to induce the expression of the immediate-early genes (IEGs) c-fos and z if/268 in striatal neurones. Another IEG, junB, is of interest because it may be involved in the suppression, rather than the enhancement, o f downstream gene transcription. in this study, rat striatal tissue wa s assayed for IEG expression by in situ hybridisation, after the injec tion of haloperidol (1 mg/kg) or fluphenazine (3 mg/kg). In addition t o c-fos mRNA and zif/268 mRNA, neurones in both the striatum and nucle us accumbens were found to contain high levels of junB mRNA, after tre atment with either haloperidol or fluphenazine. The proportion of stri atal neurones expressing junB mRNA strongly suggests that induction oc curs in striatal projection neurones. A significant increase in the le vels of the mRNA encoding another IEG, junD, was also detected after h aloperidol treatment. The atypical neuroleptic clozapine (3 mg/kg) did not induce the expression of any of these IEGs in striatal tissue. Th e results show additional complexity in the pattern of IEG induction a fter neuroleptic administration and suggest that junB is involved in m ediating some of the effects of neuroleptics on striatal gene expressi on.