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Effect of supraspinal antisense oligodeoxynucleotide treatment on delta-opioid receptor mRNA levels in mice
1Department of Pharmacology, Cornell University Medical College, New York, NY 10021, USA.
Abstract:
Studies in vivo demonstrate that antisense oligodeoxynucleotide (ODN) treatment specifically reduces the functions mediated by numerous central nervous system (CNS) receptors, including opioid receptors. However, the effects of antisense ODN on the opioid receptor mRNA target, itself are rarely examined. In the present study, the effect of supraspinal antisense ODN administration on delta-opioid receptor (DOR) mRNA levels in selected CNS regions, was investigated in mice. ODN targeting a 20-nucleotide sequence of the DOR mRNA transcript was administered by intracerebroventricular (i.c.v.) injection twice daily for 3 days. First, to confirm that antisense ODN treatment decreases DOR function in this system, antinociception produced by DOR-selective agonist [D-Ala2]deltorphin II was assessed on day 4. A 2-fold reduction in [D-Ala2]deltorphin II potency was revealed in antisense ODN-treated mice compared to mice receiving control treatments. DOR mRNA levels in selected CNS regions which either mediate antinociception; medial thalamus (MThal), periaqueductal gray (PAG), frontal cortex (FCtx) and spinal cord (SpC) or exhibit relatively high levels of DOR mRNA; nucleus accumbens (Acb) and caudate-putamen (CPu) were then quantitated by solution hybridization. Levels of DOR mRNA in antisense ODN-treated mice were not different from levels in mice treated with saline vehicle, which ranged from 0.07 pg/microg total RNA in MThal and PAG to 0.26 pg/microg total RNA in CPu. These results are both consistent with previous reports that antisense oligodeoxynucleotide (ODN) treatment down-regulates DOR protein in vivo and indicate that this down-regulation is not associated with altered DOR mRNA levels.
Insights
Antisense oligodeoxynucleotide (ODN) treatment reduced delta-opioid receptor (DOR) function but did not alter DOR mRNA levels in the mouse central nervous system (CNS). This suggests DOR protein down-regulation occurs post-transcriptionally.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- Antisense oligodeoxynucleotides (ODNs) are known to reduce central nervous system (CNS) receptor functions, including opioid receptors.
- The impact of antisense ODN on opioid receptor mRNA levels has been infrequently studied.
Purpose of the Study:
- To investigate the effect of supraspinal antisense ODN administration on delta-opioid receptor (DOR) mRNA levels in specific CNS regions of mice.
- To determine if observed reductions in DOR function correlate with changes in DOR mRNA expression.
Main Methods:
- Antisense ODN targeting DOR mRNA was administered via intracerebroventricular (i.c.v.) injection twice daily for 3 days in mice.
- DOR function was assessed by measuring antinociception using a DOR-selective agonist ([D-Ala2]deltorphin II).
- DOR mRNA levels in brain regions (medial thalamus, periaqueductal gray, frontal cortex, nucleus accumbens, caudate-putamen) and spinal cord were quantified using solution hybridization.
Main Results:
- Antisense ODN treatment led to a 2-fold reduction in the potency of the DOR-selective agonist, confirming decreased DOR function.
- No significant differences in DOR mRNA levels were found between antisense ODN-treated mice and control groups.
- DOR mRNA levels varied across CNS regions, ranging from 0.07 pg/microg total RNA to 0.26 pg/microg total RNA.
Conclusions:
- Antisense ODN treatment effectively down-regulates delta-opioid receptor (DOR) protein function in vivo.
- This functional down-regulation of DOR is not associated with changes in DOR mRNA levels, suggesting post-transcriptional regulation.