Downregulation of μ-opioid receptor mRNA in the mediobasal hypothalamus of the female guinea pig following morphine treatment

O. K. Rønnekleiv, M. A. Bosch, M. J. Cunningham, E. J. Wagner, D. K. Grandy, M. J. Kelly

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37 Scopus citations


Ribonuclease protection assays were performed on the basal hypothalamus (BH), the preoptic area (POA) and the thalamus (THAL) from female guinea pigs that were ovariectomized and implanted with morphine (n = 8) or placebo (n = 8) pellets for 1 week. An antisense [32P]rUTP labeled riboprobe, representing a 280 bp fragment of the guinea pig μ-opioid receptor gene (spanning putative TM II through eight residues of TM IV), protected a single RNA band of 280 bp. In contrast to the rat, the guinea pig THAL expressed less μ-opioid receptor mRNA than both POA and BH. Morphine treatment caused a significant decrease (15.6 ± 5.8%) in μ-opioid receptor mRNA expression in the BH, while POA and THAL were not different from placebo controls. Therefore, in conjunction with our previous findings of a downregulation of μ-opioid receptors, μ-opioid receptor mRNA is downregulated in the mediobasal hypothalamus of female guinea pigs following chronic morphine treatment.

Original languageEnglish (US)
Pages (from-to)129-132
Number of pages4
JournalNeuroscience Letters
Issue number2
StatePublished - Sep 27 1996



  • Hypothalamus
  • Morphine
  • Ribonuclease protection assay
  • Thalamus
  • Tolerance
  • μ-Opioid receptor mRNA

ASJC Scopus subject areas

  • Neuroscience(all)

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