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Mu and delta opioid-stimulated [35S]GTP gamma S binding in brain and spinal cord of polyarthritic rats

Diana L Cichewicz1, Melinda L Cox, Sandra P Welch

  • 1Department of Pharmacology and Toxicology, Virginia Commonwealth University MCV Campus, Richmond, VA 23298, USA.

European Journal of Pharmacology
|October 28, 2004
PubMed

Insights

Polyarthritis in rats alters delta opioid receptor function in the spinal cord, but not in the brain. This study investigated opioid receptor-stimulated G-protein activity in adjuvant-induced polyarthritis.

Area of Science:

  • Neuroscience
  • Pharmacology
  • Immunology

Background:

  • Complete Freund's adjuvant (CFA) injection induces polyarthritis in rats, altering opioid peptides but not opioid receptor binding.
  • Understanding changes in opioid receptor signaling is crucial for pain management in inflammatory conditions.

Purpose of the Study:

  • To measure mu and delta opioid receptor-stimulated G-protein activity in the brain and spinal cord of rats with polyarthritis.
  • To investigate the functional consequences of polyarthritis on opioid receptor signaling pathways.

Main Methods:

  • Rats were injected with CFA or vehicle to induce polyarthritis.
  • G-protein activity was measured using [35S]GTPgammaS binding assays via autoradiography in specific brain regions and the spinal cord.
  • Measurements were taken 19 days post-injection.

Main Results:

  • Mu and delta opioid receptor-stimulated G-protein activity in the caudate-putamen, medial thalamus, and periaqueductal gray remained unchanged in polyarthritic rats.
  • Delta opioid receptor-stimulated G-protein activity was significantly decreased in the spinal cord of polyarthritic rats.
  • Mu opioid receptor-stimulated activity in the spinal cord was not significantly altered.

Conclusions:

  • Polyarthritis selectively alters the functional activity of delta opioid receptors in the spinal cord.
  • These findings suggest a potential role for spinal delta opioid receptor dysfunction in the pathophysiology of polyarthritis-related pain.

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