title: Activation of glycine site and GluN2B subunit of NMDA receptors is necessary for ERK/CREB signaling cascade in rostral anterior cingulate cortex in rats: implications for affective pain.
abstract: OBJECTIVE
  The rostral anterior cingulate cortex (rACC) is implicated in processing the emotional component of pain. N-methyl-D-aspartate receptors (NMDARs) are highly expressed in the rACC and mediate pain-related affect by activating a signaling pathway that involves cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) and/or extracellular regulated kinase (ERK)/cAMP-response element-binding protein (CREB). The present study investigated the contributions of the NMDAR glycine site and GluN2B subunit to the activation of ERK and CREB both in vitro and in vivo in rat rACC.
  
  
  METHODS
  Immunohistochemistry and Western blot analysis were used to separately assess the expression of phospho-ERK (pERK) and phospho-CREB (pCREB) in vitro and in vivo. Double immunostaining was also used to determine the colocalization of pERK and pCREB.
  
  
  RESULTS
  Both bath application of NMDA in brain slices in vitro and intraplantar injection of formalin into the rat hindpaw in vivo induced significant up-regulation of pERK and pCREB in the rACC, which was inhibited by the NMDAR antagonist DL-2-amino-5-phospho-novaleric acid. Selective blockade of the NMDAR GluN2B subunit and the glycine-binding site, or degradation of endogenous D-serine, a co-agonist for the glycine site, significantly decreased the up-regulation of pERK and pCREB expression in the rACC. Further, the activated ERK predominantly colocalized with CREB.
  
  
  CONCLUSIONS
  Either the glycine site or the GluN2B subunit of NMDARs participates in the phosphorylation of ERK and CREB induced by bath application of NMDA in brain slices or hindpaw injection of 5% formalin in rats, and these might be fundamental molecular mechanisms underlying pain affect.
authors.affiliation: Institutes of Neurobiology, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Cao
authors.forename: Wen-Hua
authors.initials: WH
authors.lastname: Ren
authors.forename: Mu-Ye
authors.initials: MY
authors.lastname: Zhu
authors.forename: Zhi-Qi
authors.initials: ZQ
authors.lastname: Zhao
authors.forename: Yu-Qiu
authors.initials: YQ
authors.lastname: Zhang
mesh_terms: D000818:Animals; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005998:Glycine / Q000502:physiology; D006179:Gyrus Cinguli / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D016202:N-Methylaspartate / Q000378:metabolism / Q000494:pharmacology; D010146:Pain / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; C121001:NR2B NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate; D048049:Extracellular Signal-Regulated MAP Kinases; D005998:Glycine