Synaptic localization of NMDA receptor subunits in the rat retina

J Comp Neurol. 2000 Apr 24;420(1):98-112.


The distribution and synaptic clustering of N-methyl-D-aspartate (NMDA) receptors were studied in the rat retina by using subunit specific antisera. A punctate immunofluorescence was observed in the inner plexiform layer (IPL) for all subunits tested, and electron microscopy confirmed that the immunoreactive puncta represent labeling of receptors clustered at postsynaptic sites. Double labeling of sections revealed that NMDA receptor clusters within the IPL are composed of different subunit combinations: NR1/NR2A, NR1/NR2B, and in a small number of synapses NR1/NR2A/NR2B. The majority of NMDA receptor clusters were colocalized with the postsynaptic density proteins PSD-95, PSD-93, and SAP 102. Double labeling of the NMDA receptor subunit specific antisera with protein kinase C (PKC), a marker of rod bipolar cells, revealed very little colocalization at the rod bipolar cell axon terminal. This suggests that NMDA receptors are important in mediating neurotransmission within the cone bipolar cell pathways of the IPL. The postsynaptic neurons are a subset of amacrine cells and most ganglion cells. Usually only one of the two postsynaptic processes at the bipolar cell ribbon synapses expressed NMDA receptors. In the outer plexiform layer (OPL), punctate immunofluoresence was observed for the NR1C2; subunit, which was shown by electron microscopy to be localized presynaptically within both rod and cone photoreceptor terminals.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Disks Large Homolog 4 Protein
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Nerve Tissue Proteins / metabolism
  • Rats
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Retina / metabolism*
  • Retina / ultrastructure
  • Retinal Cone Photoreceptor Cells / metabolism
  • Retinal Cone Photoreceptor Cells / ultrastructure
  • Retinal Rod Photoreceptor Cells / metabolism*
  • Retinal Rod Photoreceptor Cells / ultrastructure
  • Synapses / metabolism*
  • Synapses / ultrastructure


  • Disks Large Homolog 4 Protein
  • Dlg4 protein, rat
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Mpp2 protein, rat
  • NMDA receptor A1
  • NR2A NMDA receptor
  • NR2B NMDA receptor
  • Nerve Tissue Proteins
  • Receptors, N-Methyl-D-Aspartate
  • postsynaptic density proteins