Switching of NMDA receptor 2A and 2B subunits at thalamic and cortical synapses during early postnatal development.
Switching of the NMDA receptor 2A (NR2A) and NR2B subunits at NMDA receptors is thought to underlie the functional changes that occur in NMDA receptor properties during the developmental epoch when neural plasticity is most pronounced. The cellular expression of NR2A and NR2B and the NR2 synaptic binding protein postsynaptic density-95 (PSD-95) was examined in the mouse somatosensory cortex and thalamus from postnatal day 2 (P2) to P15 using reverse transcription-PCR, in situ hybridization histochemistry, and immunocytochemistry. The localization of NR2A and NR2B subunits and PSD-95 was then studied at synapses in layer IV of somatosensory cortex and in the ventral posterior nucleus of the thalamus using high-resolution immunoelectron microscopy. At both cortical and thalamic synapses, a quantitative switch in the dominant synaptic subunit from NR2B to NR2A was accompanied by a similar change in the cellular expression of NR2A but not of NR2B. Synaptic PSD-95 developed independently, although both NR2A and NR2B colocalized with PSD-95. Displacement of NR2B subunits from synapses was not accompanied by an increase in an extrasynaptic pool of this subunit. Thus, the switch in synaptic NR2 subunit predominance does not occur by changes in expression or displacement from synapses and may reflect the formation of new synapses from which NR2B is lacking.
Center for Neuroscience, University of California, Davis, California 95616, USA.
Xiao-Bo
XB
Liu
Karl D
KD
Murray
Edward G
EG
Jones
D000818:Animals; D000076122:Disks Large Homolog 4 Protein; D051528:Guanylate Kinases; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051379:Mice; D008813:Mice, Inbred ICR; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000378:metabolism; D021122:Protein Subunits / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D013003:Somatosensory Cortex / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D013569:Synapses / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D013788:Thalamus / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*
D000076122:Disks Large Homolog 4 Protein; D051528:Guanylate Kinases; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D021122:Protein Subunits; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; C501447:Dlg4 protein, mouse; C121001:NR2B NMDA receptor; C033652:postsynaptic density proteins