Calcium-independent release of [ [formula omitted]]spermine from chick retina

Spermine has been shown to influence NMDA receptor function through an interaction at the coagonist site for glycine in the central nervous system (CNS) and the retina. In order to support a role for spermine as neurotransmitter or neuromodulator in the chick retina, specific stimulated-release of s...

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Bibliographic Details
Published in:Brain research 2000-01, Vol.854 (1), p.1-5
Main Authors: CALDERON, F, RODRIGUEZ, G, LOPEZ, E, LOPEZ-COLOME, A. M
Format: Article
Language:English
Subjects:
Animals
Animals, Newborn
Biological and medical sciences
Calcium - physiology
Chick retina
Chickens
Digitoxigenin - pharmacology
Enzyme Inhibitors - pharmacology
Excitatory Amino Acid Agonists - pharmacology
Eye and associated structures. Visual pathways and centers. Vision
Fundamental and applied biological sciences. Psychology
In Vitro Techniques
N-Methylaspartate - pharmacology
NMDA receptor
Ouabain - pharmacology
Potassium Chloride - pharmacology
Retina - metabolism
Sodium - metabolism
Sodium-Potassium-Exchanging ATPase - antagonists & inhibitors
Spermine
Spermine - metabolism
Tritium
Vertebrates: nervous system and sense organs
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Summary:Spermine has been shown to influence NMDA receptor function through an interaction at the coagonist site for glycine in the central nervous system (CNS) and the retina. In order to support a role for spermine as neurotransmitter or neuromodulator in the chick retina, specific stimulated-release of spermine should be demonstrated. Isolated chick retinas, preloaded with [ 3 H ]spermine, were stimulated with 1 mM NMDA and other glutamate agonists at ionotropic receptors, in a continuous superfusion system. [ 3 H ]spermine was released from the retina by depolarization with 50 mM KCl, in a Ca 2+-independent manner. Inhibition of Na +/K +-ATPase by ouabain or digitoxigenin also induced spermine release following 36 min in the presence of the drugs; such effect seems unrelated to changes in Na + electrochemical gradients, since nigericin and veratrine did not induce release in Na + containing medium. The lack of effect of glutamate, NMDA and kainate at 1 mM concentration, suggests that release of spermine in the retina is mediated by the reversal of uptake and not necessarily linked to EAA-receptor activation.
ISSN:0006-8993
1872-6240
DOI:10.1016/S0006-8993(99)02157-5