Intracellular mGluR5 plays a critical role in neuropathic pain

Nat Commun. 2016 Feb 3;7:10604. doi: 10.1038/ncomms10604.

Abstract

Spinal mGluR5 is a key mediator of neuroplasticity underlying persistent pain. Although brain mGluR5 is localized on cell surface and intracellular membranes, neither the presence nor physiological role of spinal intracellular mGluR5 is established. Here we show that in spinal dorsal horn neurons >80% of mGluR5 is intracellular, of which ∼60% is located on nuclear membranes, where activation leads to sustained Ca(2+) responses. Nerve injury inducing nociceptive hypersensitivity also increases the expression of nuclear mGluR5 and receptor-mediated phosphorylated-ERK1/2, Arc/Arg3.1 and c-fos. Spinal blockade of intracellular mGluR5 reduces neuropathic pain behaviours and signalling molecules, whereas blockade of cell-surface mGluR5 has little effect. Decreasing intracellular glutamate via blocking EAAT-3, mimics the effects of intracellular mGluR5 antagonism. These findings show a direct link between an intracellular GPCR and behavioural expression in vivo. Blockade of intracellular mGluR5 represents a new strategy for the development of effective therapies for persistent pain.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics, Opioid / pharmacology
  • Animals
  • Behavior, Animal*
  • Blotting, Western
  • Calcium / metabolism*
  • Cells, Cultured
  • Cytoskeletal Proteins / metabolism
  • Excitatory Amino Acid Transporter 3 / antagonists & inhibitors
  • Glutamic Acid / metabolism*
  • Glutamic Acid / pharmacology
  • Hyperalgesia / metabolism*
  • Hyperalgesia / pathology
  • Immunohistochemistry
  • Injections, Spinal
  • Male
  • Microdialysis
  • Microscopy, Confocal
  • Microscopy, Electron
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Morphine / pharmacology
  • Nerve Tissue Proteins / metabolism
  • Neuralgia / metabolism*
  • Posterior Horn Cells / metabolism*
  • Posterior Horn Cells / pathology
  • Proto-Oncogene Proteins c-fos / metabolism
  • Proto-Oncogene Proteins c-jun / metabolism
  • Rats
  • Rats, Long-Evans
  • Receptor, Metabotropic Glutamate 5 / metabolism*
  • Sciatic Nerve / injuries
  • Sciatic Neuropathy / metabolism*
  • Sciatic Neuropathy / pathology

Substances

  • Analgesics, Opioid
  • Cytoskeletal Proteins
  • Excitatory Amino Acid Transporter 3
  • Grm5 protein, rat
  • Nerve Tissue Proteins
  • Proto-Oncogene Proteins c-fos
  • Proto-Oncogene Proteins c-jun
  • Receptor, Metabotropic Glutamate 5
  • activity regulated cytoskeletal-associated protein
  • Glutamic Acid
  • Morphine
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Calcium