title: PKMζ is essential for spinal plasticity underlying the maintenance of persistent pain.
abstract: BACKGROUND
  Chronic pain occurs when normally protective acute pain becomes pathologically persistent. We examined here whether an isoform of protein kinase C (PKC), PKMζ, that underlies long-term memory storage in various brain regions, also sustains nociceptive plasticity in spinal cord dorsal horn (SCDH) mediating persistent pain.
  
  
  RESULTS
  Cutaneous injury or spinal stimulation produced persistent increases of PKMζ, but not other atypical PKCs in SCDH. Inhibiting spinal PKMζ, but not full-length PKCs, reversed plasticity-dependent persistent painful responses to hind paw formalin and secondary mechanical hypersensitivity and SCDH neuron sensitization after hind paw capsaicin, without affecting peripheral sensitization-dependent primary heat hypersensitivity after hind paw capsaicin. Inhibiting spinal PKMζ, but not full-length PKCs, also reversed mechanical hypersensitivity in the rat hind paw induced by spinal stimulation with intrathecal dihydroxyphenylglycine. Spinal PKMζ inhibition also alleviated allodynia 3 weeks after ischemic injury in rats with chronic post-ischemia pain (CPIP), at a point when allodynia depends on spinal changes. In contrast, spinal PKMζ inhibition did not affect allodynia in rats with chronic contriction injury (CCI) of the sciatic nerve, or CPIP rats early after ischemic injury, when allodynia depends on ongoing peripheral inputs.
  
  
  CONCLUSIONS
  These results suggest spinal PKMζ is essential for the maintenance of persistent pain by sustaining spinal nociceptive plasticity.
authors.affiliation: Department of Anesthesia, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, H3G 1Y6, Canada.
authors.forename: Andre
authors.initials: A
authors.lastname: Laferrière
authors.forename: Mark H
authors.initials: MH
authors.lastname: Pitcher
authors.forename: Anne
authors.initials: A
authors.lastname: Haldane
authors.forename: Yue
authors.initials: Y
authors.lastname: Huang
authors.forename: Virginia
authors.initials: V
authors.lastname: Cornea
authors.forename: Naresh
authors.initials: N
authors.lastname: Kumar
authors.forename: Todd C
authors.initials: TC
authors.lastname: Sacktor
authors.forename: Fernando
authors.initials: F
authors.lastname: Cervero
authors.forename: Terence J
authors.initials: TJ
authors.lastname: Coderre
mesh_terms: D000818:Animals; D059350:Chronic Pain / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology; D009619:Nociceptors / Q000378:metabolism; D010147:Pain Measurement; D020671:Posterior Horn Cells / Q000378:metabolism / Q000503:physiopathology; D011493:Protein Kinase C / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D013116:Spinal Cord / Q000378:metabolism* / Q000503:physiopathology
chemical_list: D011493:Protein Kinase C; C504730:protein kinase M zeta, rat