Retinal NMDA receptors

Martins R. A., Silveira M. S., Curado M. R., Police A. I., and Linden R. (2005). NMDA receptor activation modulates programmed cell death during early post-natal retinal development a BDNF-dependent mechanism. J. Neurochem. 95 244-253. 

Sucher N. J., Lei S. Z., and Lipton S. A. (1991). Calcium channel antagonists attenuate NMDA receptor-mediated neurotoxicity of retinal ganglion cells in culture. Brain Res. 297 297-302. 

Russo, R., Cavaliere, F., Berliocchi, L., Nucci, C., Gliozzi, M., Mazzei, C., Tassorelli, C., Corasaniti, M. T., Rotiroti, D., Bagetta, G., and Morrone, L. A. (2008a). Modulation of pro-survival and death-associated pathways under retinal ischemia/reperfusion Effects of NMDA receptor blockade. 

Retinal circuitry is further refined by ehminating inappropriate synapses. Glutamate, through NMDA receptors, is known to be involved in synaptic pruning in the CNS, and there is evidence that it also does so in the retina. 

Glutamate s role as a neurotransmitter in the vertebrate retina is reviewed by Barnstable (1993), Brandstatter et al. (1998) and Lo et al. (1998). As the cell bodies of different retinal cell types are in different laminae (Fig. 10), we can assign which general cell types express which glutamate receptor subunits. However, there are different subsets of the same cell class, e.g., there are at least 10 different types of on- and off-bipolars, and multiple subtypes of the other cell classes (Stevens, 1998). Without cell-type markers and double-labelling studies, ISH can not differentiate these. The cones and rods release glutamate onto the bipolar cells only off-bipolars use ionotropic receptors at this synapse on-bipolars use the metabotropic receptor mGluR6 instead. The distribution of NMDA and non-NMDA receptor mRNAs in the retina is summarized in Fig. 10. 

Puro DG, Yuan JP, Sucher NJ (1996) Activation of NMDA receptor-channels in human retinal Muller glial cells inhibits inward-rectifying potassium currents. Vis Neurosci 73 319-326. 

Diamond JA, Copenhagen DR. The contribution of NMDA and non-NMDA receptors to the light-evoked input-output characteristics of retinal ganglion cells. Neuron 1993 11 725-738. 

Retinal ganglion cells are the output cells of the refina. Their axons course along the vitreal surface of the refina and bundle together to exit the eye as the optic nerve. Ganglion cells are excited by glutamate released from bipolar cells acting on both NMDA and non-NMDA (KA- and AMPA-type) glutamate receptors (Thoreson and Witkovsky, 1999). 

Retinal ischemic injury, for example, has been shown to result in the overstimulation of ionotropic glutamate receptors following the extracellular accumulation of glutamate (18,19). This effect appears to involve, in particular, the NMDA class of glutamate receptors. The subsequent excessive influx of calcium results in... 

Cohen ED, Miller RF. The role of NMDA and non-NMDA excitatory amino acid receptors in the functional organization of primate retinal ganglion cells. Vis Neurosci 1994 11 317-332. 

---