Assessment of delta opioid antinociception and receptor mRNA levels in mouse after chronic naltrexone treatment

Assessment of delta opioid antinociception and receptor mRNA levels in mouse after chronic... The antinociceptive potency of the delta opioid receptor (DOR) agonist (D-Ala 2 )Deltorphin II and the levels of DOR mRNA were measured in mice chronically treated with naltrexone. ED 50 determinations for (D-Ala 2 )Deltorphin II, using the tail-flick test with mice that had been treated with naltrexone for 7 days followed by a 24 h naltrexone free period (study day 8), revealed a 7.7-fold increase in antinociceptive potency, indicating functional supersensitivity. Utilization of a micro-dissection technique followed by quantitative solution hybridization measurements of RNA extracts from mouse CNS revealed levels of DOR mRNA ranging from 2.8 pg/μg RNA in the caudate-putamen to 0.3 pg/μg RNA in cerebellum. However, despite the functional increase in DOR sensitivity, the DOR mRNA levels in selected brain areas and spinal cord of naltrexone-treated and control mice did not differ. Assessment of DOR mRNA levels in whole brain and selected CNS regions after shorter treatment intervals (1, 6 and 12 h and 2 and 7 days) in naltrexone-treated and control mice revealed a similar pattern of results. Northern blot analysis of mouse whole brain RNA extracts after 7 days of naltrexone treatment did not show any alteration in the size of the DOR transcript. These data demonstrate that DOR mRNA levels are not altered during and after chronic naltrexone treatment and therefore are not associated with opioid-induced DOR up-regulation or DOR functional supersensitivity. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Brain Research Elsevier

Assessment of delta opioid antinociception and receptor mRNA levels in mouse after chronic naltrexone treatment

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Publisher
Elsevier
Copyright
Copyright © 1995 Elsevier Ltd
ISSN
0006-8993
D.O.I.
10.1016/0006-8993(95)00615-W
Publisher site
See Article on Publisher Site

Abstract

The antinociceptive potency of the delta opioid receptor (DOR) agonist (D-Ala 2 )Deltorphin II and the levels of DOR mRNA were measured in mice chronically treated with naltrexone. ED 50 determinations for (D-Ala 2 )Deltorphin II, using the tail-flick test with mice that had been treated with naltrexone for 7 days followed by a 24 h naltrexone free period (study day 8), revealed a 7.7-fold increase in antinociceptive potency, indicating functional supersensitivity. Utilization of a micro-dissection technique followed by quantitative solution hybridization measurements of RNA extracts from mouse CNS revealed levels of DOR mRNA ranging from 2.8 pg/μg RNA in the caudate-putamen to 0.3 pg/μg RNA in cerebellum. However, despite the functional increase in DOR sensitivity, the DOR mRNA levels in selected brain areas and spinal cord of naltrexone-treated and control mice did not differ. Assessment of DOR mRNA levels in whole brain and selected CNS regions after shorter treatment intervals (1, 6 and 12 h and 2 and 7 days) in naltrexone-treated and control mice revealed a similar pattern of results. Northern blot analysis of mouse whole brain RNA extracts after 7 days of naltrexone treatment did not show any alteration in the size of the DOR transcript. These data demonstrate that DOR mRNA levels are not altered during and after chronic naltrexone treatment and therefore are not associated with opioid-induced DOR up-regulation or DOR functional supersensitivity.

Journal

Brain ResearchElsevier

Published: Sep 11, 1995

References

  • Supraspinal delta opioid receptor mRNA levels are not altered in (D-Ala 2 )Deltorphin II tolerant mice
    Kest, B.; Jenab, S.; Brodsky, M.; Elliott, K.; Inturrisi, C.E.

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