title: Phosphorylation of ERK in neurokinin 1 receptor-expressing neurons in laminae III and IV of the rat spinal dorsal horn following noxious stimulation.
abstract: BACKGROUND
  There is a population of large neurons with cell bodies in laminae III and IV of the spinal dorsal horn which express the neurokinin 1 receptor (NK1r) and have dendrites that enter the superficial laminae. Although it has been shown that these are all projection neurons and that they are innervated by substance P-containing (nociceptive) primary afferents, we know little about their responses to noxious stimuli. In this study we have looked for phosphorylation of extracellular signal-regulated kinases (ERKs) in these neurons in response to different types of noxious stimulus applied to one hindlimb of anaesthetised rats. The stimuli were mechanical (repeated pinching), thermal (immersion in water at 52 degrees C) or chemical (injection of 2% formaldehyde).
  
  
  RESULTS
  Five minutes after each type of stimulus we observed numerous cells with phosphorylated ERK (pERK) in laminae I and IIo, together with scattered positive cells in deeper laminae. We found that virtually all of the lamina III/IV NK1r-immunoreactive neurons contained pERK after each of these stimuli and that in the great majority of cases there was internalisation of the NK1r on the dorsal dendrites of these cells. In addition, we also saw neurons in lamina III that were pERK-positive but lacked the NK1r, and these were particularly evident in animals that had had the pinch stimulus.
  
  
  CONCLUSIONS
  Our results demonstrate that lamina III/IV NK1r-immunoreactive neurons show receptor internalisation and ERK phosphorylation after mechanical, thermal or chemical noxious stimuli.
authors.affiliation: Spinal Cord Group, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK. e.polgar@bio.gla.ac.uk
authors.forename: Erika
authors.initials: E
authors.lastname: Polgár
authors.forename: Annie D
authors.initials: AD
authors.lastname: Campbell
authors.forename: Lynsey M
authors.initials: LM
authors.lastname: MacIntyre
authors.forename: Masahiko
authors.initials: M
authors.lastname: Watanabe
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Todd
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D005557:Formaldehyde; D006358:Hot Temperature; D007150:Immunohistochemistry; D008159:Lumbar Vertebrae; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000276:immunology / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000276:immunology / Q000378:metabolism*; D009676:Noxae; D010147:Pain Measurement; D010766:Phosphorylation; D010812:Physical Stimulation; D020671:Posterior Horn Cells / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018040:Receptors, Neurokinin-1 / Q000276:immunology / Q000378:metabolism*; D013268:Stimulation, Chemical
chemical_list: D000911:Antibodies, Monoclonal; D009676:Noxae; D018040:Receptors, Neurokinin-1; D005557:Formaldehyde; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3