Estrogen status and psychophysical stress modify temporomandibular joint input to medullary dorsal horn neurons in a lamina-specific manner in female rats

Keiichiro Okamoto, Randall Thompson, Ayano Katagiri, David A. Bereiter

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Estrogen status and psychological stress contribute to the expression of several chronic pain conditions including temporomandibular muscle and joint disorders (TMJD). Sensory neurons that supply the temporomandibular joint (TMJ) region terminate in laminae I and V of the spinal trigeminal nucleus (Vc/C 1-2 region); however, little is known about lamina-specificity and environmental influences on the encoding properties of TMJ brainstem neurons. To test the hypothesis that Vc/C1-2 neurons integrate both interoceptive and exteroceptive signals relevant for TMJ nociception, we recorded TMJ-evoked activity in superficial and deep laminae of ovariectomized rats under high and low estradiol (E2) and stress conditions. Rats received daily injections of low (LE) or high (HE) dose E2 and were subjected to forced swim (FS) or sham swim conditioning for 3 days. The results revealed marked lamina-specificity in that HE rats displayed enhanced TMJ-evoked activity in superficial, but not deep, laminae independent of stress conditioning. By contrast, FS conditioned rats displayed increased background firing and TMJ-evoked activity of neurons in deep, but not superficial, laminae independent of E2 status. FS also enhanced TMJ-evoked masseter muscle activity and suggested the importance of deep dorsal horn neurons in mediating evoked jaw muscle activity. In conclusion, E2 status and psychophysical stress play a significant role in modifying the encoding properties of TMJ-responsive medullary dorsal horn neurons with a marked lamina-specificity.

Original languageEnglish (US)
Pages (from-to)1057-1064
Number of pages8
JournalPain
Volume154
Issue number7
DOIs
StatePublished - Jul 2013

Keywords

  • Estradiol
  • Forced swim conditioning
  • Nociception
  • Temporomandibular joint
  • Trigeminal subnucleus caudalis

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