Functional interactions between NMDA receptors and TRPV1 in trigeminal sensory neurons mediate mechanical hyperalgesia in the rat masseter muscle

Pain. 2012 Jul;153(7):1514-1524. doi: 10.1016/j.pain.2012.04.015. Epub 2012 May 19.

Abstract

The NMDA and TRPV1 receptors that are expressed in sensory neurons have been independently demonstrated to play important roles in peripheral pain mechanisms. In the present study, we investigated whether the 2 receptor-channel systems form a functional complex that provides the basis for the development of mechanical hyperalgesia. In the masseter muscle, direct application of NMDA induced a time-dependent increase in mechanical sensitivity, which was significantly blocked when the muscle was pretreated with a specific TRPV1 antagonist, AMG9810. The NR1 subunit of the NMDA receptor and TRPV1 were coexpressed in 32% of masseter afferents in trigeminal ganglia (TG). Furthermore, NR1 and NR2B formed protein-protein complexes with TRPV1 in TG as demonstrated by coimmunoprecipitation experiments. Calcium imaging analyses further corroborated that NMDA and TRPV1 receptors functionally interact. In TG culture, application of NMDA resulted in phosphorylation of serine, but not threonine or tyrosine, residues of TRPV1 in a time course similar to that of the development of NMDA-induced mechanical hyperalgesia. The NMDA-induced phosphorylation was significantly attenuated by CaMKII and PKC inhibitors, but not by a PKA inhibitor. Consistent with the biochemical data, the NMDA-induced mechanical hyperalgesia was also effectively blocked when the muscle was pretreated with a CaMKII or PKC inhibitor. Thus, NMDA receptors and TRPV1 functionally interact via CaMKII and PKC signaling cascades and contribute to mechanical hyperalgesia. These data offer novel mechanisms by which 2 ligand-gated channels in sensory neurons interact and reinforce the notion that TRPV1 functions as a signal integrator under pathological conditions.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acrylamides / pharmacology
  • Animals
  • Bridged Bicyclo Compounds, Heterocyclic / pharmacology
  • Calcium / metabolism
  • Hyperalgesia / physiopathology*
  • Male
  • Masseter Muscle / drug effects
  • Masseter Muscle / metabolism*
  • Pain Measurement
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Sensory Receptor Cells / drug effects
  • Sensory Receptor Cells / metabolism*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • TRPV Cation Channels / antagonists & inhibitors
  • TRPV Cation Channels / metabolism*
  • Trigeminal Ganglion / metabolism
  • Trigeminal Ganglion / physiopathology

Substances

  • 3-(4-t-butylphenyl)-N-(2,3-dihydrobenzo(b)(1,4)dioxin-6-yl)acrylamide
  • Acrylamides
  • Bridged Bicyclo Compounds, Heterocyclic
  • Receptors, N-Methyl-D-Aspartate
  • TRPV Cation Channels
  • Trpv1 protein, rat
  • Calcium