Abstract
Acute blockade of dopamine D2 receptors by the typical antipsychotic drug haloperidol leads to alterations in neuronal gene expression and behavior. In the dorsolateral striatum, the levels of mRNA for the immediate-early gene c-fos and the neuropeptide gene neurotensin/neuromedin N (NT/N) are significantly increased by haloperidol. An acute behavioral response to haloperidol is catalepsy, considered to be a rodent correlate of some of the immediate extrapyramidal motor side effects seen in humans. Several lines of evidence suggest a link between neurotensin induction in the dorsolateral striatum and catalepsy. We hypothesize that both striatal gene induction and catalepsy elicited by haloperidol arise from the combined effect of excitatory adenosinergic and glutamatergic inputs acting at adenosine A2A andN-methyl-d-aspartate (NMDA) receptors, respectively. In agreement with our previous reports, adenosine antagonists reduced haloperidol-induced c-fos and neurotensin gene expression as well as catalepsy. In agreement with other reports, the noncompetitive NMDA receptor antagonist MK-801 also reduced gene expression and catalepsy in response to haloperidol. The competitive NMDA receptor antagonist LY235959 decreased haloperidol-induced catalepsy. We show here that blocking both A2A and NMDA receptors simultaneously in conjunction with haloperidol resulted in a combined effect on gene expression and behavior that was greater than that for block of either receptor alone. Both c-fos and NT/N mRNA levels were reduced, and catalepsy was completely abolished. These results indicate that the haloperidol-induced increases in c-fos and NT gene expression in the dorsolateral striatum and catalepsy are driven largely by adenosine and glutamatergic inputs acting at A2Aand NMDA receptors.
Footnotes
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Send reprint requests to: Elena H. Chartoff, Box 356560, Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA. E-mail: echartof{at}u.washington.edu
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↵1 This work was supported by the National Alliance for Research on Schizophrenia and Depression Distinguished Investigator Grant to D.M.D.
- Abbreviations:
- HAL
- haloperidol
- DLSt
- dorsolateral striatum
- NT/N
- neurotensin/neuromedin N
- ROD
- relative optical density
- PKA
- protein kinase A
- MCID
- microcomputer imaging device
- NMDA
- N-methyl-d-aspartate
- CSC
- 8-(3-chlorostyryl)-caffeine
- SSC
- standard saline citrate
- EPS
- extrapyramidal symptoms
- Received February 5, 1999.
- Accepted July 19, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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