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Central mu opioid receptor mechanisms modulate mustard oil-evoked jaw muscle activity

C H Tambeli1, K Seo, B J Sessle

  • 1Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, Ontario, Canada M5G 1G6.

Brain Research
|September 5, 2001
PubMed

Insights

Mustard oil injection into the temporomandibular joint (TMJ) region of rats increases jaw muscle activity. This nociceptive reflex is enhanced by naloxone, suggesting modulation by endogenous opioid inhibitory mechanisms.

Area of Science:

  • Neuroscience
  • Pain Research
  • Mammalian Physiology

Background:

  • Temporomandibular joint (TMJ) pain is a common condition.
  • Inflammatory irritants can trigger persistent pain signals.
  • Endogenous opioid systems play a role in pain modulation.

Purpose of the Study:

  • To investigate the effect of mustard oil (MO) on jaw muscle activity in rats.
  • To explore the role of endogenous opioid mechanisms in modulating MO-induced nociception in the TMJ region.

Main Methods:

  • Rats were injected with mustard oil (MO) into the TMJ region.
  • Electromyographic (EMG) activity of jaw muscles was recorded.
  • Intrathecal (i.t.) administration of opioid antagonists (naloxone, mu, delta, kappa selective) was performed.

Main Results:

  • Mustard oil injection caused a sustained and reversible increase in jaw muscle EMG activity.
  • Intrathecal naloxone and mu-selective opioid antagonists 'rekindled' the nociceptive reflex.
  • Delta and kappa-selective opioid antagonists did not significantly affect the reflex.

Conclusions:

  • Mustard oil induces a robust nociceptive reflex in the TMJ region.
  • Endogenous opioid inhibitory mechanisms, particularly involving mu-opioid receptors, modulate this nociceptive reflex.

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