Journal of Neuroscience, Vol 12, 652-663, Copyright © 1992 by Society for Neuroscience
Differential effects of haloperidol and clozapine on neurotensin gene transcription in rat neostriatum
KM Merchant, PR Dobner and DM Dorsa
Department of Pharmacology, University of Washington, Seattle 98195.
A single dose of typical neuroleptic, haloperidol, has been demonstrated to
increase the expression of neurotensin/neuromedin N (NT/N) mRNA in the
dorsolateral striatum within 1 hr of its administration (Merchant et al.,
1991). The present study further investigated neuroleptic-induced
regulation of NT/N gene transcription. Levels of NT/N mRNA were examined at
various times following a single dose of haloperidol (1 mg/kg, i.p.) or the
atypical antipsychotic clozapine (20, 30, or 40 mg/kg, i.p.) by in situ
hybridization histochemistry and quantitative solution hybridization. In
the dorsolateral striatum, the two drugs had strikingly different effects;
haloperidol rapidly (within 30 min) increased the expression of mature NT/N
mRNA while virtually no increase was observed in response to nontoxic doses
of clozapine at any of the time points examined. Following haloperidol,
maximal induction occurred at 7 hr, at which time NT/N mRNA levels were an
order of magnitude higher than basal levels. By 20 hr after haloperidol,
there was a significant decline in striatal NT/N mRNA levels. In situ
hybridization analysis using an intron-derived probe revealed that
haloperidol-induced increases in mature NT/N mRNA levels in the striatum
were preceded by a transient increase in intron-containing NT/N gene
transcripts. These data strongly indicate that acute haloperidol treatment
results in transient transcriptional activation of NT/N gene, although a
concomitant effect on the stability of NT/N primary transcripts cannot be
ruled out. In contrast to their differential effects in the dorsolateral
striatum, a single dose of both haloperidol and clozapine induced a small
but significant increase in NT/N mRNA expression in the shell sector of the
nucleus accumbens. These results raise the possibility that NT neurons in
the nucleus accumbens may, at least in part, mediate the antipsychotic
effects of classical neuroleptics, whereas NT cells in the dorsolateral
region of the striatum may be involved in mediating other effects of
typical neuroleptics such as extrapyramidal motor symptoms.