PUBLICATION
Transport-mediated release of endogenous glutamate in the vertebrate retina
- Authors
- Maguire, G., Simko, H., Weinreb, R.N., and Ayoub, G.
- ID
- ZDB-PUB-990108-4
- Date
- 1998
- Source
- Pflugers Archiv : European journal of physiology 436: 481-484 (Journal)
- Registered Authors
- Maguire, Giselle
- Keywords
- none
- MeSH Terms
-
- ATP-Binding Cassette Transporters/metabolism
- Amino Acid Transport System X-AG
- Animals
- Biological Transport
- Calcium/metabolism
- Extracellular Space/metabolism
- Fluorometry
- Glutamic Acid/metabolism*
- Potassium/metabolism
- Retina/metabolism*
- Retina/ultrastructure
- Retinal Ganglion Cells/metabolism
- Retinal Ganglion Cells/ultrastructure
- Zebrafish
- PubMed
- 9644233 Full text @ Pflügers Archiv. / Eur. J. Physiol.
Citation
Maguire, G., Simko, H., Weinreb, R.N., and Ayoub, G. (1998) Transport-mediated release of endogenous glutamate in the vertebrate retina. Pflugers Archiv : European journal of physiology. 436:481-484.
Abstract
In the present study we measured calcium-dependent, vesicular glutamate release, and calcium-independent, transport-mediated glutamate release patterns in the vertebrate retina to better understand the sources of elevated glutamate in neural tissue under ischemic conditions. A potassium concentration of 40 mM, which mimics the extracellular potassium concentration in the central nervous system during ischemia, was applied to the bathing medium of a retinal slice prepared from zebrafish. High external potassium evoked release of endogenous glutamate that was measured using a glutamate-specific fluorometric assay applied to the bath. The slice was visualized under 668 nm light using Normarski optics and fluorescent images were captured using a cooled charge-coupled device (CCD) camera. Following the elevation of external potassium to 40 mM several bands of glutamate fluorescence, reflecting the spatial distribution of glutamate release, were observed. A calcium-dependent cloud of glutamate was observed in the inner plexiform layer, that was antagonized by bath-applied nifedipine. A relatively dense glutamate cloud (1-10 microM) was observed over the ganglion cell layer, which was blocked by dihydrokainate, a glutamate transport antagonist. In contrast, nifedipine, an inhibitor of calcium-dependent neurotransmitter release in the retina, failed to block the cloud of released glutamate in the ganglion cell layer. These data suggest that under pathological conditions in the eye where glutamate levels are elevated surrounding retinal ganglion cells, such as observed in some forms of glaucoma, a possible source of the elevated glutamate is through a glutamate transporter operating in a reversed direction. A likely candidate for mediating this reversed transport of glutamate is the retinal Muller cell.
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Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Orthology
Engineered Foreign Genes
Mapping