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Light-evoked increases in extracellular K+ in the plexiform layers of amphibian retinas.
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MedLine Citation:
PMID:  3876405     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Recordings of light-evoked changes in extracellular K+ concentration (delta[K+]o) were obtained in the retinas of frog and mudpuppy. In eyecup preparations, various recording approaches were used and provided evidence for a K increase near the outer plexiform layer (distal K increase). This distal K increase could be pharmacologically dissociated from the well-known, large K increase in the proximal retina by the application of ethanol and gamma-aminobutyric acid. The distal K increase also often showed surround antagonism. A retinal slice preparation was used to permit electrode placement into the desired retinal layers under direct visual control and without the risk of electrode damage to adjacent layers. In the slice, a distinct distal K increase was found in the outer plexiform layer, in addition to the prominent K increase in the inner plexiform layer. Compared with eyecups, only weak K increases were found in the nuclear layers of the slice. This suggests that the K responses observed in the nuclear layers of eyecups may be generated by K+ diffusing along the electrode track from the plexiform layers. In the context of current models of ERG b-wave generation, the magnitude of the recorded distal K increase, compared with the proximal K increase, seems too small to give rise to the b-wave. However, the distal K increase may be differentially depressed by electrode dead space. It is also possible that if certain aspects of the models of b-wave generation were modified, then the observed distal K increase could give rise to the b-wave.
Authors:
C J Karwoski; E A Newman; H Shimazaki; L M Proenza
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of general physiology     Volume:  86     ISSN:  0022-1295     ISO Abbreviation:  J. Gen. Physiol.     Publication Date:  1985 Aug 
Date Detail:
Created Date:  1985-11-01     Completed Date:  1985-11-01     Revised Date:  2008-11-20    
Medline Journal Info:
Nlm Unique ID:  2985110R     Medline TA:  J Gen Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  189-213     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Extracellular Space / metabolism*
Light*
Microelectrodes
Necturus maculosus
Potassium / metabolism*
Rana pipiens
Retina / metabolism*
Valinomycin
Grant Support
ID/Acronym/Agency:
EY 03526/EY/NEI NIH HHS; EY 04077/EY/NEI NIH HHS
Chemical
Reg. No./Substance:
2001-95-8/Valinomycin; 7440-09-7/Potassium

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

Full Text
Journal Information
Journal ID (nlm-ta): J Gen Physiol
ISSN: 0022-1295
ISSN: 1540-7748
Publisher: The Rockefeller University Press
Article Information
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Print publication date: Day: 1 Month: 8 Year: 1985
Volume: 86 Issue: 2
First Page: 189 Last Page: 213
ID: 2228783
Publisher Id: 86010207
PubMed Id: 3876405

Light-evoked increases in extracellular K+ in the plexiform layers of amphibian retinas


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