Distribution of glutamate receptor subtypes in the vertebrate retina.
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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ABSTRACT: Excitotoxicity has been proposed to play a pivotal role in retinal ischemia. Retinal ischemia-associated ocular disorders are vision threatening. The aim was to also examine whether and how S-allyl L-cysteine (SAC) can protect the retina against kainate excitotoxicity. In vivo retinal excitotoxicity was induced by an intravitreous injection of 100 μM kainate into a Wistar rat eye for 1 day. The management and mechanisms involved in the processes were evaluated by electrophysiology, immunohistochemistry, histopathology, and various biochemical approaches. In the present study, the cultured retinal cells were shown to possess kainate receptors. The defined retinal excitotoxic changes were characterized by a decrease in electroretinogram (ERG) b-wave amplitudes, a loss of the fluorogold retrograde labeled retinal ganglion cells (RGCs), an increase in the apoptotic cells in the RGC layer, and an increase in vimentin or glial fibrillary acidic protein (GFAP) immunoreactivity, a marker for Müller cells. An up-regulation in the mRNA levels of inducible nitric oxide synthase (iNOS) and matrix metalloproteinases-9 (MMPs-9) was also detected in the retina subjected to kainate excitoxicity. Importantly, the excitotoxicity-induced alterations were significantly blunted when 100 μM SAC and/or the kainate receptor antagonist CNQX was applied. Conclusively, SAC would seem to protect the retina against kainate excitotoxicity via an inhibition of the up-regulation of iNOS and MMP-9 as well as a modulation of glial activation and apoptosis.The American Journal of Chinese Medicine 01/2014; 42(3):693-708. DOI:10.1142/S0192415X14500451 · 2.63 Impact Factor
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ABSTRACT: Schizophrenia is a complex mental disorder associated with not only cognitive dysfunctions, such as memory and attention deficits, but also changes in basic sensory processing. Although most studies on schizophrenia have focused on disturbances in higher-order brain functions associated with the prefrontal cortex or frontal cortex, recent investigations have also reported abnormalities in low-level sensory processes, such as the visual system. At very early stages of the disease, schizophrenia patients frequently describe in detail symptoms of a disturbance in various aspects of visual perception that may lead to worse clinical symptoms and decrease in quality of life. Therefore, the aim of this review is to describe the various studies that have explored the visual issues in schizophrenia.Current Psychiatry Reports 05/2015; 17(5):569. DOI:10.1007/s11920-015-0569-x · 3.05 Impact Factor
Article: Neurotransmitters in the retina[Show abstract] [Hide abstract]
ABSTRACT: Processing of visual information within the retina depends in large measure upon a complement of chemical neurotransmitters which are released at synaptic contacts between individual neurons. Numerous investigators have participated in the identification of many of these transmitters and their assignment to specific neuronal subpopulations. However, it is now clear that the action of each transmitter depends upon the receptor molecules to which it binds. Multidisciplinary studies are underway to characterize these receptors as well as to investigate transporter molecules which may serve not only to inactivate certain neurotransmitters but may also function in their release.