Group I metabotropic glutamate receptor NMDA receptor coupling and signaling cascade mediate spinal dorsal horn NMDA receptor 2B tyrosine phosphorylation associated with inflammatory hyperalgesia.
Hindpaw inflammation induces tyrosine phosphorylation (tyr-P) of the NMDA receptor (NMDAR) 2B (NR2B) subunit in the rat spinal dorsal horn that is closely related to the initiation and development of hyperalgesia. Here, we show that in rats with Freund's adjuvant-induced inflammation, the increased dorsal horn NR2B tyr-P is blocked by group I metabotropic glutamate receptor (mGluR) antagonists [7-(hydroxyimino)cyclopropa[b] chromen-1a-carboxylate ethyl ester (CPCCOEt) and 2-methyl-6-(phenylethynyl)-pyridine (MPEP), by the Src inhibitor CGP 77675, but not by the MAP kinase inhibitor 2'-amino-3'-methoxyflavone. Analysis of the calcium pathways shows that the in vivo NR2B tyr-P is blocked by an IP3 receptor antagonist 2-aminoethoxydiphenylborate (2APB) but not by antagonists of ionotropic glutamate receptors and voltage-dependent calcium channels, suggesting that the NR2B tyr-P is dependent on intracellular calcium release. In a dorsal horn slice preparation, the group I (dihydroxyphenylglycine), but not group II [(2R,4R)-4-aminopyrrolidine-2,3-dicarboxylate] and III [L-AP 4 (L-(+)-2-amino-4-phosphonobutyric acid)], mGluR agonists, an IP3 receptor (D-IP3) agonist, and a PKC (PMA) activator, induces NR2B tyr-P similar to that seen in vivo after inflammation. Coimmunoprecipitation indicates that Shank, a postsynaptic density protein associated with mGluRs, formed a complex involving PSD-95 (postsynaptic density-95), NR2B, and Src in the spinal dorsal horn. Double immunofluorescence studies indicated that NR1 is colocalized with mGluR5 in dorsal horn neurons. mGluR5 also coimmunoprecipitates with NR2B. Finally, intrathecal pretreatment of CPCCOEt, MPEP, and 2APB attenuates inflammatory hyperalgesia. Thus, inflammation and mGluR-induced NR2B tyr-P share similar mechanisms. The group ImGluR-NMDAR coupling cascade leads to phosphorylation of the NMDAR and appears necessary for the initiation of spinal dorsal horn sensitization and behavioral hyperalgesia after inflammation.
Guo
Wei
W
Department of Biomedical Sciences, Dental School and Program in Neuroscience, University of Maryland, Baltimore, Maryland 21201, USA.
Wei
Feng
F
Zou
Shiping
S
Robbins
Meredith T
MT
Sugiyo
Shinichi
S
Ikeda
Tetsuya
T
Tu
Jian-Cheng
JC
Worley
Paul F
PF
Dubner
Ronald
R
Ren
Ke
K
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005620:Freund's Adjuvant; D006614:Hindlimb / Q000294:innervation / Q000503:physiopathology; D006930:Hyperalgesia / Q000139:chemically induced / Q000150:complications / Q000378:metabolism*; D007249:Inflammation / Q000139:chemically induced / Q000150:complications / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D010766:Phosphorylation / Q000187:drug effects; D020671:Posterior Horn Cells / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D053496:Inositol 1,4,5-Trisphosphate Receptors; C121001:NR2B NMDA receptor; D018160:Receptors, Cytoplasmic and Nuclear; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D014443:Tyrosine; D005620:Freund's Adjuvant; D019061:src-Family Kinases; D011493:Protein Kinase C