title: Mammalian target of rapamycin signaling in the spinal cord is required for neuronal plasticity and behavioral hypersensitivity associated with neuropathy in the rat.
abstract: The protein kinase mammalian target of rapamycin (mTOR) regulates mRNA translation and is inhibited by rapamycin. Signaling pathways involving mTOR are implicated in physiological and pathophysiological processes. We determined the spinal effects of the rapamycin analogue cell cycle inhibitor (CCI)-779 on neuronal responses and behavioral hypersensitivity in a model of persistent neuropathic pain. We also assessed the anatomical distribution of spinal mTOR signaling pathways. Specifically, we ligated rat spinal nerves L5 and L6 to produce a model of neuropathic pain. After confirming neuropathy with behavioral testing, we obtained in vivo single-unit extracellular stimulus-evoked recordings from deep dorsal horn spinal neurons. We applied CCI-779 spinally in electrophysiological and behavioral studies and assessed its effects accordingly. We also used immunohistochemistry to probe for mTOR signaling pathways in dorsal root ganglia (DRG) and the spinal cord. We found that spinally administered CCI-779 rapidly attenuated calibrated mechanically but not thermally evoked neuronal responses and mechanically evoked behavioral responses. Immunohistochemistry showed presence of mTOR signaling pathways in nociceptive-specific C-fiber DRG and in neurons of inner lamina II of the spinal cord. We conclude that alterations in the activity of spinal mTOR signaling pathways are crucial to the full establishment of spinal neuronal plasticity and behavioral hypersensitivity associated with nerve injury.
  
  
  CONCLUSIONS
  This study is consistent with growing evidence implicating mTOR signaling pathways as important modulators of persistent pain, providing novel insights into the molecular mechanisms of pain maintenance and potential for novel approaches into treating chronic pain.
authors.affiliation: Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK. curtisasante@gmail.com
authors.forename: Curtis O
authors.initials: CO
authors.lastname: Asante
authors.forename: Victoria C
authors.initials: VC
authors.lastname: Wallace
authors.forename: Anthony H
authors.initials: AH
authors.lastname: Dickenson
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D004594:Electrophysiology; D006930:Hyperalgesia / Q000378:metabolism / Q000503:physiopathology; D007150:Immunohistochemistry; D008297:Male; D009437:Neuralgia / Q000378:metabolism* / Q000503:physiopathology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D010523:Peripheral Nervous System Diseases / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D020123:Sirolimus / Q000031:analogs & derivatives / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D013127:Spinal Nerves / Q000187:drug effects / Q000293:injuries / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D047428:Protein Kinase Inhibitors; C401859:temsirolimus; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus
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