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The antisense strategy applied to the study of dopamine D3 receptor functions in rat forebrain
M Tremblay1, C Rouillard, D Lévesque
1Unité de recherche en neuroscience, Centre Hospitalier Universitaire du Québec, Canada.
Abstract:
1. The authors have investigated the effects of a dopamine D3 receptor antisense oligodeoxynucleotide (ODN), on neuropeptides (neurotensin and dynorphin) and transcription factor (c-fos) mRNA levels in rat forebrain. 2. Intracerebroventricular injections of ODNs were made into the lateral ventricle (5 and 10 micrograms/h, for 5 days). Effect of antisense administration on dopamine D2 and D3 receptor binding were measured by means of receptor autoradiography. Neuropeptides and c-fos mRNA levels were evaluated by in situ hybridization using specific complementary RNA probes. 3. Dopamine D3 receptor densities were dose-dependently reduced in the shell of nucleus accumbens of rats that received the D3 antisense ODN. Sense and missense controls remained without effect. No significant effect was observed on D2 receptor binding in any of the ODN groups studied, as measured with [3H]raclopride binding. Concomitant reductions of dynorphin and neurotensin mRNA levels were observed in the shell of nucleus accumbens after D3 antisense ODN administration. Interestingly, the D3 antisense administration also reduced c-fos mRNA levels in the cingulate cortex of these animals. 4. The results show that D3 receptors may tonically regulate basal transcription factor, as well as neuropeptides, gene expression in the rat forebrain. These results clearly demonstrate that an antisense strategy could be useful to identify molecular targets under control of specific dopamine receptor subtypes.
Insights
Dopamine D3 receptor antisense oligodeoxynucleotide (ODN) reduced neurotensin, dynorphin, and c-fos mRNA levels in rat forebrain. This indicates D3 receptors tonically regulate gene expression, suggesting antisense strategies for targeting dopamine receptors.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- Dopamine receptors, particularly the D3 subtype, play crucial roles in regulating gene expression.
- Understanding the specific functions of dopamine receptor subtypes is essential for developing targeted therapies.
Purpose of the Study:
- To investigate the effects of a dopamine D3 receptor antisense oligodeoxynucleotide (ODN) on neuropeptide and transcription factor mRNA levels in the rat forebrain.
- To determine if D3 receptors tonically regulate gene expression and to assess the utility of antisense strategies in this context.
Main Methods:
- Intracerebroventricular injections of D3 receptor antisense ODN in rats.
- Measurement of dopamine D2 and D3 receptor binding using receptor autoradiography.
- Evaluation of neuropeptide (neurotensin, dynorphin) and c-fos mRNA levels via in situ hybridization.
Main Results:
- Dose-dependent reduction in dopamine D3 receptor densities in the nucleus accumbens shell following D3 antisense ODN administration.
- Significant decreases in dynorphin and neurotensin mRNA levels in the nucleus accumbens shell.
- Reduced c-fos mRNA levels observed in the cingulate cortex after D3 antisense ODN treatment.
- No significant effects on D2 receptor binding were detected.
Conclusions:
- Dopamine D3 receptors appear to exert tonic regulation over basal transcription factor and neuropeptide gene expression in the rat forebrain.
- Antisense strategies represent a viable approach for identifying molecular targets regulated by specific dopamine receptor subtypes.