Opioid peptides and receptors in joint tissues: Study in the rat

Jonas Bergström, Mahmood Ahmed, Jian Li, Tashfeen Ahmad, Andris Kreicbergs, Mariana Spetea

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24 Citations (Scopus)


Using immunohistochemical and biochemical techniques, the occurrence of endogenous opioid peptides and their receptors in normal rat bone and joint tissues was investigated. Opioid receptors were detected, quantified, and characterized in homogenates from capsule/synovium and periosteum using radioligand binding assays. Receptor binding of the nonselective opioid [3H]naloxone to tissue homogenates was stereospecific and saturable, showing similar characteristics to that of brain tissue, although with lower binding capacities. By immunohistochemistry, the neuronal occurrence of four different enkephalins was demonstrated in synovium, bone marrow, periosteum, and juxta-articular bone, whereas no neuronal dynorphin immunoreactivity was detected. Double-staining studies disclosed that enkephalins coexisted with substance P in primary afferent fibers. The applied techniques can be used to assess changes in the distribution of endogenous opioids and their receptors in joint tissues in conditions associated with pain and inflammation. The endogenous opioid system now demonstrated might be targeted and exploited therapeutically to obtain peripheral control of symptoms in joint disorders.

Original languageEnglish
Pages (from-to)1193-1199
Number of pages7
JournalJournal of Orthopaedic Research
Issue number6
Publication statusPublished - Jun 2006
Externally publishedYes


  • Binding assay
  • Immunohistochemistry
  • Joint tissue
  • Opioid peptide
  • Opioid receptor


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