Document Detail

Glutamate spillover between mammalian cone photoreceptors.
MedLine Citation:
PMID:  21940436     Owner:  NLM     Status:  MEDLINE    
Cone photoreceptors transmit signals at high temporal frequencies and mediate fine spatial vision. High-frequency transmission requires a high rate of glutamate release, which could promote spillover to neighboring cells, whereas spatial vision requires that cones within a tightly packed array signal light to postsynaptic bipolar cells with minimal crosstalk. Glutamate spread from the cone terminal is thought to be limited by presynaptic transporters and nearby glial processes. In addition, there is no ultrastructural evidence for chemical synapses between mammalian cones, although such synapses have been described in lower vertebrate retinas. We tested for cone-cone glutamate diffusion by recording from adjacent cone pairs in the ground squirrel retina, and instead found that the glutamate released by one cone during electrical stimulation activates glutamate transporter Cl(-) conductances on neighboring cones. Unlike in other systems, where crosstalk is diminished by increasing the temperature and by moving to a more intact preparation, glutamate spread persisted at physiological temperatures (37°C) and in retinal flat mounts. The glutamate-gated anion conductance in cones has a reversal potential of ∼-30 mV compared with a cone resting potential of ∼-50 mV; thus, crosstalk should have a depolarizing effect on the cone network. Cone-cone glutamate spread is regulated by the physiological stimulus, light, and under physiological conditions can produce a response of ∼2 mV, equivalent to 13-20% of a cone's light response. We conclude that in the absence of discrete chemical synapses, glutamate flows between cones during a light response and may mediate a spatially distributed positive feedback.
Brett A Szmajda; Steven H Devries
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of neuroscience : the official journal of the Society for Neuroscience     Volume:  31     ISSN:  1529-2401     ISO Abbreviation:  J. Neurosci.     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-09-23     Completed Date:  2011-12-07     Revised Date:  2014-09-15    
Medline Journal Info:
Nlm Unique ID:  8102140     Medline TA:  J Neurosci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  13431-41     Citation Subset:  IM    
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MeSH Terms
Amino Acid Transport System X-AG / physiology
Chloride Channels / physiology
Electric Stimulation / methods
Glutamic Acid / metabolism*
Membrane Potentials / physiology
Patch-Clamp Techniques / methods
Photic Stimulation / methods
Receptor Cross-Talk / physiology
Retina / metabolism,  physiology
Retinal Cone Photoreceptor Cells / metabolism*
Synaptic Transmission / physiology*
Vision, Ocular / physiology*
Grant Support
EY012141/EY/NEI NIH HHS; R01 EY012141/EY/NEI NIH HHS; R01 EY012141-12S1/EY/NEI NIH HHS; R01 EY012141-15/EY/NEI NIH HHS
Reg. No./Substance:
0/Amino Acid Transport System X-AG; 0/Chloride Channels; 0/glutamate-gated chloride channels; 3KX376GY7L/Glutamic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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