title: Two N-methyl-D-aspartate receptors in rat dorsal root ganglia with different subunit composition and localization.
abstract: N-methyl-D-aspartate (NMDA) receptors in sensory afferents participate in chronic pain by mediating peripheral and central sensitization. We studied the presence of NMDA receptor subunits in different types of primary afferents. Western blots indicated that rat dorsal root ganglia (DRG) contain NR1, NR2B, NR2C, and NR2D but not NR2A. Real-time RT-PCR showed that NR2B and NR2D were expressed at higher levels than NR2A and NR2C in DRG. Immunofluorescence with an antibody that recognized NR1 and another that recognized NR2A and NR2B showed that NR1 and NR2B colocalized in 90% of DRG neurons, including most A-fibers (identified by the presence of neurofilament 200 kDa). In contrast, an antibody recognizing NR2C and NR2D labeled only neurofilament-negative DRG profiles. This antibody stained practically all DRG cells that contained calcitonin gene-related peptide and neurokinins and those that bound isolectin B4. The percentage of cells immunoreactive for NR1, NR2A/NR2B, and NR2C/NR2D were the same in the T9, T12, L4, and L6 DRG. The intracellular distribution of the NR2 subunits was strikingly different: Whereas NR2A/NR2B immunoreactivity was found in the Golgi apparatus and occasionally at the plasma membrane, NR2C/NR2D immunoreactivity was found in the cytoplasm but not in the Golgi. The NR1 subunit was present throughout the cytoplasm and was more intense in the Golgi. These findings indicate that DRG neurons have two different NMDA receptors, one containing the NR1, NR2D, and possibly the NR2C subunits, found only in C-fibers, and the diheteromer NR1/NR2B, present in the Golgi apparatus of both A- and C-fibers.
authors.affiliation: Neuroenteric Disease Program, CURE: Digestive Diseases Research Center, Department of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA. marvizon@ucla.edu
authors.forename: Juan Carlos G
authors.initials: JC
authors.lastname: Marvizón
authors.forename: James A
authors.initials: JA
authors.lastname: McRoberts
authors.forename: Helena S
authors.initials: HS
authors.lastname: Ennes
authors.forename: Bingbing
authors.initials: B
authors.lastname: Song
authors.forename: Xueren
authors.initials: X
authors.lastname: Wang
authors.forename: Lisa
authors.initials: L
authors.lastname: Jinton
authors.forename: Brit
authors.initials: B
authors.lastname: Corneliussen
authors.forename: Emeran A
authors.initials: EA
authors.lastname: Mayer
mesh_terms: D000818:Animals; D000918:Antibody Specificity / Q000276:immunology; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology*; D002908:Chronic Disease; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D037102:Lectins / Q000378:metabolism; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism* / Q000648:ultrastructure; D009413:Nerve Fibers, Myelinated / Q000378:metabolism* / Q000648:ultrastructure; D016900:Neurofilament Proteins / Q000378:metabolism; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism*; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure; D010146:Pain / Q000378:metabolism / Q000503:physiopathology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley / Q000033:anatomy & histology / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism*; D015320:Tachykinins / Q000378:metabolism
chemical_list: D037102:Lectins; C409466:NR1 NMDA receptor; C120997:NR2A NMDA receptor; C121001:NR2B NMDA receptor; C432823:NR2C NMDA receptor; D016900:Neurofilament Proteins; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D015320:Tachykinins; C051774:neurofilament protein H; D015740:Calcitonin Gene-Related Peptide