title: Systemic administration of propentofylline, ibudilast, and (+)-naltrexone each reverses mechanical allodynia in a novel rat model of central neuropathic pain.
abstract: Central neuropathic pain (CNP) is a debilitating consequence of central nervous system damage for which current treatments are ineffective. To explore mechanisms underlying CNP, we developed a rat model involving T13/L1 dorsal root avulsion. The resultant dorsal horn damage creates bilateral below-level (L4-L6) mechanical allodynia. This allodynia, termed spinal neuropathic avulsion pain, occurs in the absence of confounding paralysis. To characterize this model, we undertook a series of studies aimed at defining whether spinal neuropathic avulsion pain could be reversed by any of 3 putative glial activation inhibitors, each with distinct mechanisms of action. Indeed, the phosphodiesterase inhibitor propentofylline, the macrophage migration inhibitory factor inhibitor ibudilast, and the toll-like receptor 4 antagonist (+)-naltrexone each reversed below-level allodynia bilaterally. Strikingly, none of these impacted spinal neuropathic avulsion pain upon first administration but required 1 to 2 weeks of daily administration before pain reversal was obtained. Given reversal of CNP by each of these glial modulatory agents, these results suggest that glia contribute to the maintenance of such pain and enduring release of macrophage migration inhibitory factor and endogenous agonists of toll-like receptor 4 is important for sustaining CNP. The markedly delayed efficacy of all 3 glial modulatory drugs may prove instructive for interpretation of apparent drug failures after shorter dosing regimens.
  
  
  CONCLUSIONS
  CNP that develops after trauma is often described by patients as severe and intolerable. Unfortunately, current treatments are not effective. This work suggests that using pharmacologic treatments that target glial cells could be an effective clinical treatment for CNP.
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado. Electronic address: ellisal@colorado.edu.
authors.forename: Amanda
authors.initials: A
authors.lastname: Ellis
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado.
authors.forename: Julie
authors.initials: J
authors.lastname: Wieseler
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado.
authors.forename: Jacob
authors.initials: J
authors.lastname: Favret
authors.affiliation: Medicinova, San Diego, California.
authors.forename: Kirk W
authors.initials: KW
authors.lastname: Johnson
authors.affiliation: Chemical Biology Research Branch, National Institute on Drug Abuse and National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland.
authors.forename: Kenner C
authors.initials: KC
authors.lastname: Rice
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado.
authors.forename: Steven F
authors.initials: SF
authors.lastname: Maier
authors.affiliation: Craig Hospital, Englewood, Colorado.
authors.forename: Scott
authors.initials: S
authors.lastname: Falci
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado.
authors.forename: Linda R
authors.initials: LR
authors.lastname: Watkins
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006930:Hyperalgesia / Q000209:etiology*; D008297:Male; D009271:Naltrexone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009437:Neuralgia / Q000209:etiology*; D009457:Neuroglia / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011843:Radiculopathy / Q000150:complications; D051381:Rats; D017207:Rats, Sprague-Dawley; D014970:Xanthines / Q000494:pharmacology; D007212:Indolizines; D011720:Pyrazoles
chemical_list: D009271:Naltrexone; D009292:Narcotic Antagonists; D018696:Neuroprotective Agents; D010726:Phosphodiesterase Inhibitors; D011725:Pyridines; D014970:Xanthines; C032114:propentofylline; C038366:ibudilast; D007212:Indolizines; D011720:Pyrazoles
keywords: Avulsion; d-naltrexone; glia; pain; toll-like receptor 4