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Inhibition of microglial P2X4 receptors attenuates morphine tolerance, Iba1, GFAP and mu opioid receptor protein

Ryan J Horvath1, Alfonso E Romero-Sandoval, Joyce A De Leo

  • 1Department of Pharmacology, Dartmouth Medical School, Hanover, NH 03755, USA Neuroscience Center at Dartmouth, Lebanon, NH 03756, USA Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.

Pain
|June 25, 2010
PubMed

Insights

Targeting P2X4 receptors on microglia can block opioid tolerance and reduce glial activation. This offers a potential new strategy to improve pain management for chronic pain patients.

Area of Science:

  • Neuroscience
  • Pharmacology
  • Immunology

Background:

  • Opioid anti-nociceptive tolerance limits chronic pain treatment efficacy.
  • Glial cells, particularly microglia, play a key role in opioid tolerance development.
  • Morphine enhances microglial activation and migration via mu opioid receptor signaling.

Purpose of the Study:

  • To investigate the role of P2X4 receptors in morphine tolerance and spinal glial reactivity.
  • To determine if P2X4 receptors mediate morphine-induced changes in microglia and perivascular microglia.
  • To explore P2X4 receptor modulation as a therapeutic strategy for opioid tolerance.

Main Methods:

  • Rats received chronic morphine via osmotic minipumps.
  • P2X4 receptor antisense oligonucleotide (asODN) was administered intrathecally to inhibit P2X4 receptor expression.
  • Morphine-induced changes in P2X4 receptor expression, glial markers (Iba1, GFAP), mu opioid receptor expression, and perivascular microglial ED2 expression were assessed.

Main Results:

  • P2X4 receptor asODN treatment blocked morphine-induced P2X4 receptor expression and prevented anti-nociceptive tolerance.
  • P2X4 receptor asODN attenuated morphine-dependent increases in spinal Iba1, GFAP, and mu opioid receptor expression.
  • Chronic morphine decreased perivascular microglial ED2 expression, which was reversed by P2X4 receptor asODN treatment.

Conclusions:

  • P2X4 receptors are critical drivers of morphine tolerance and spinal glial activation.
  • Modulating P2X4 receptor expression on microglia and perivascular microglia may be a viable adjuvant therapy to mitigate opioid-induced anti-nociceptive tolerance.
  • Targeting P2X4 receptors offers a promising avenue for improving long-term opioid efficacy in pain management.

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