Localization and developmental expression of the NMDA receptor subunit NR2A in the mammalian retina

Abstract

The localization of the N-methyl-D-aspartate receptor subunit NRBA was studied, by using light microscopic immunocytochemistry, in the retina of adult rat, rabbit, cat, and monkey. Strong, punctate immunolabeling was observed in the inner plexiform layer indicating a synaptic localization of the NRZA subunit. The punctate labeling was concentrated in two bands corresponding to the on-and off-sublaminae of the inner plexiform layer.The punctate character of immunofluorescence suggested a synaptic localization of the receptor. This was confirmed by electron microscopy of immunostained adult rat retina. The staining was localized postsynaptic to cone bipolar cells, and only one of the two postsynaptic elements of the dyad was labeled. Staining was not observed at extrasynaptic plasma membranes.In situ hybridization of adult rat retina showed expression of the NRZA subunit in virtually all ganglion cells and displaced amacrine cells in the ganglion cell layer and in a subset of amacrine cells in the inner nuclear layer.The postnatal developmental expression of the NRZA subunit was studied in rat retina by light microscopic immunocytochemistry. Punctate immunolabeling appeared prior to eye opening, and the developmental profile of NRZA could be compatible with a role in development of circuitry in the inner plexiform layer. I 1994 wiley-Liss, Inc.

Group I Metabotropic Glutamate Receptors mGluR1α and mGluR5a: Localization in Both Synaptic Layers of the Rat Retina

“…3A). Punctate distribution of the mGluR5a receptor staining at the light microscopic level indicated synaptic localization, as was shown for several other types of neurotransmitter receptors in the retina (Pourcho and Owczarzak, 1991;Yazulla and Studholme, 1991;Grünert and Wässle, 1993;Hartveit et al, 1994;Brandstätter et al, 1996). The diffuse labeling on putative bipolar cell somata in the INL, however, also showed extrasynaptic localization of mGluR5a immunolabel.…”

Distinct perisynaptic and synaptic localization of NMDA and AMPA receptors on ganglion cells in rat retina

“…For example, extrasynaptic NMDARs contain primarily the NR2B subunit, while NR2A-containing receptors are located primarily in the PSD (Tovar & Westbrook 1999;Hartveit et al, 1994). Preliminary data indicates that NR2B-containing receptors contribute to lightevoked EPSCs (T. Kalbaugh and S. Chen, unpublished), prompting us to use a cocktail of NR1 and NR2B antibodies.…”

“…NMDARs encounter a lower glutamate concentration during evoked EPSCs than do NMDARs and an NMDAR component emerges in mEPSCs when glutamate uptake is reduced (Chen and Diamond, 2002), suggesting that NMDARs may be located extrasynaptically on RGC dendrites (see also Matsui et al, 1998). This is in apparent contrast to pre-embedding EM studies in mammalian retina indicating that NMDAR subunits are present in postsynaptic elements at cone bipolar cell ribbon synapses (Hartveit et al, 1994;Fletcher et al, 2000;Pourcho et al, 2001). These studies did not determine the identity of the immunopositive postsynaptic process, however, and the preembedding immunoperoxidase method, which allows reaction product to diffuse throughout the immunopositive process, precludes distinction between localization to the PSD versus the immediately surrounding extrasynaptic membrane (Ottersen and Landsend, 1997;Nusser, 2000;Bredt and Nicoll, 2003).…”

Ionotropic glutamate receptors of amacrine cells of the mouse retina

“…The clusters immunostained for the different subunits show characteristic distributions across the inner plexiform layer IPL!, suggesting they are involved with different sets of neurons Hartveit et al, 1994;Peng et al, 1995;Brandstätter et al, 1998;Thoreson & Witkovsky, 1999;Fletcher et al, 2000;Hack et al, 2001;Grünert et al, 2002!. The two postsynaptic partners at the bipolar cell dyad usually express two different types of GluRs Brandstätter et al, 1994;Qin & Pourcho, 1996, 1999a2001!. A more detailed analysis has been performed examining the GluRs postsynaptic to the rod bipolar cell dyad showing that AMPA receptors are localized to the AII cell, while d102 subunits are found on the A17 cell~Ghosh et al, 2001;Li et al, 2002! have studied the glutamatergic drive of different neurons in the retina with a channel-permeant guanidinium analogue~1-amino-4-guanidobutane, AGB!…”

“…tested showed KA receptor-mediated responses. Although KA receptor subunits have been found by immunocytochemistry throughout the IPL of the mammalian retinã rat: Brandstätter et al, 1994Brandstätter et al, , 1997cat: Qin & Pourcho, 2001;mouse: Haverkamp & Wässle, 2000;monkey: Grünert al., 2002!, to our knowledge this is the first study to report KA receptor activity in amacrine cells. However, comparable to the expression of AMPA receptors we also observed a great variability in the expression of KA receptors.…”