Article

Distribution of glutamate receptor subtypes in the vertebrate retina

Johns Hopkins University, Baltimore, Maryland, United States
Neuroscience (Impact Factor: 3.33). 06/1995; 66(2):483-97. DOI: 10.1016/0306-4522(94)00569-Q
Source: PubMed

ABSTRACT The distribution of glutamate receptor subunit/subtypes in the vertebrate retina was investigated by immunocytochemistry using anti-peptide antibodies against AMPA (GluR1-4), kainate (GluR6/7) and metabotropic (mGluR1 alpha) receptors. All receptor subtypes examined are present in the mammalian retina, but they are distributed differentially. GluR1 is present in the inner plexiform layer as well as amacrine and ganglion cell bodies. GluR2 is present mainly in the outer plexiform layer and bipolar cells. An anti-GluR2/3 antibody labels both plexiform layers and various cell bodies in the inner nuclear layer and the ganglion cell layer. GluR4 is present on Müller glial cells. In the goldfish retina, GluR2 immunoreactivity is prominent in the Mb type of ON-bipolar cells, including the dendrites and the large synaptic terminal. The putative dendritic localization is surprising, because no depolarizing conductance increase induced by glutamate is thought to be present in these cells. An AMPA receptor at a presynaptic terminal is also unusual, and probably provides feedback control of glutamate release. GluR6/7 is most widespread in the retina, being present in horizontal, bipolar, amacrine and ganglion cells. Ion channels composed of GluR6 are now known to be phosphorylated by protein kinase A, resulting in current potentiation. This property and our present observation together suggest that the glutamate receptors previously studied electrophysiologically by others in horizontal cells may contain GluR6. mGluR1 alpha is found mostly in the inner plexiform layer; its localization partially overlaps with that of the inositol trisphosphate receptor in the retina. Our results suggest that, in the retina, glutamate receptor subtypes may be expressed in selective cell types according to their specific functions.

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    • "Immunostaining and electron microscopic studies in the rat retina have shown that mGlu1 receptors are present in the dendrites of rod bipolar cells and in amacrine cell processes postsynaptic to axon terminals of OFF-cone, ON-cone and rod bipolar cells [17]. From their material they were not able to say whether ganglion cell dendrites were also labeled for mGlu1 receptors, although in an earlier study [23] a few large ganglion cell bodies in the rat retina were found to be immunostained for mGlu1 receptors. In the cat retina [24], the immunostaining pattern for mGlu1 receptors is similar to what Koulen et al. [17] observed in the rat retina, with two notable exceptions: 1) the synaptic terminals of rod photoreceptors but not the dendrites of rod bipolar cells were labeled, and 2) no labeling of amacrine cell processes postsynaptic to axon terminals of rod bipolar cells were observed. "
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    • "reno et al . , 1998 ; Watabe et al . , 2002 ; White et al . , 2003 ) . Direct ultrastructural evidence of mGluR 1 on presynaptic retinogeniculate terminals is lacking , but these cells are positive for mGluR 1 , however it is not clear whether the receptors are only within the dendritic arbor and not in axonal terminals ( Hartveit et al . , 1995 ; Peng et al . , 1995 ; Tehrani et al . , 2000 ) . The mechanisms underlying the presynaptic actions of mGluRs in inhibiting glutamate release and physiological implications are unclear . It has been hypothesized that the mGluRs are coupled to inhibitory pathway where activation of mGluR 1 inhibit glutamate release following desensitization ( Rodriguez - Mor"
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