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Stimulation of photoreceptor disc shedding and pigment epithelial phagocytosis by glutamate, aspartate, and other amino acids. J Comp Neurol 1985 Sep 22;239(4):361-72 PMID: 2864363

Pubmed ID

2864363

Abstract

It has been reported that aspartate and glutamate selectively impair the structure (Olney, '82) and function (e.g., Furakawa and Hanawa, '55) of second- and third-order retinal neurons while leaving the photoreceptor unaffected. Either amino acid may mimic the endogenous photoreceptor neurotransmitter (Ehinger, '82). We report here that excitatory amino acids also induce massive rod photoreceptor disc shedding in eyecups of Xenopus laevis maintained in vitro. Disc shedding is the process whereby photoreceptors eliminate effete discs. It involves interaction between the distal outer segment and pigment epithelium. Millimolar L-aspartate and L-glutamate, as well as micromolar kainic acid, a glutamate analog, stimulate disc shedding three- to fivefold higher than normal light-evoked shedding levels and result in extensive inner retinal damage. Fifty-millimolar KCl, 1.0 microM ouabain, and replacement of sodium with choline also stimulate disc shedding and alter retinal structure. Extensive neurotoxicity appears unrelated to disc shedding since other amino acids having no significant or marginal effects on retinal structure also stimulate shedding. While the site and mechanism of action of these effectors, and in particular the excitatory amino acids, is now undefined, the data show that amino acids thought to act directly and specifically on inner retinal neurons can also markedly alter photoreceptor and pigment epithelial metabolism.

Author List

Greenberger LM, Besharse JC

Author

Joseph C. Besharse PhD Director, Professor in the Ophthalmology and Visual Sciences department at Medical College of Wisconsin




Scopus

2-s2.0-0021972398   43 Citations

MESH terms used to index this publication - Major topics in bold

Amino Acids
Animals
Aspartic Acid
Cell Membrane
Choline
Dose-Response Relationship, Drug
Glutamates
Glutamic Acid
Kainic Acid
Kinetics
Organ Culture Techniques
Ouabain
Phagocytosis
Photic Stimulation
Photoreceptor Cells
Pigment Epithelium of Eye
Potassium Chloride
Xenopus laevis
jenkins-FCD Prod-353 9ccd8489072cb19f5b9f808bb23ed672c582f41e