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Increased intracellular sodium mimics some but not all aspects of photoreceptor adaptation in the ventral eye of Limulus.
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MedLine Citation:
PMID:  591914     Owner:  NLM     Status:  MEDLINE    
The effects of the intracellular iontophoretic injection of Na+ ions have been quantitatively compared with adaptation in ventral photoreceptors of Limulus. We find that: (a) both light adaptation and sodium injection are associated with a decrease in the variability of the threshold response amplitued; (b) both light adaptation and sodium injection are associated with a decrease in the absolute value of the temporal dispersion of the threshold response time delay; (c) the same template curve adequately fits the intensity response relationships measured under light adaptation and Na+ injection; (d) both light adaptation and Na+ injection produce a fourfold decrease in response time delay for a desensitization of 3 log units; (e) the time coures of light adaptation and dark adaptation is significantly faster than the onset of and recovery from desensitization produced by Na+ injection; (f) unlike local illumination, Na+ injection does not produce localized desensitization of the photoreceptor. These findings suggest that a rise in intracellular Na+ concentration makes at most only a minor contribution (probably less than 5%) to the total adaptation of these receptors in the intensity range we have examined (up to 3 log units above absolute threshold). However, changes in intracellular Na+ concentration may contribute to certain components of light and dark adaptation in these receptors.
A Fein; J S Charlton
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of general physiology     Volume:  70     ISSN:  0022-1295     ISO Abbreviation:  J. Gen. Physiol.     Publication Date:  1977 Nov 
Date Detail:
Created Date:  1978-02-18     Completed Date:  1978-02-18     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2985110R     Medline TA:  J Gen Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  601-20     Citation Subset:  IM    
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MeSH Terms
Action Potentials / drug effects
Adaptation, Ocular*
Dark Adaptation
Electric Stimulation
Horseshoe Crabs
Membrane Potentials / drug effects
Ocular Physiological Phenomena
Photoreceptor Cells / drug effects,  physiology*
Sodium / administration & dosage,  pharmacology*,  physiology
Time Factors
Reg. No./Substance:

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: 11 Year: 1977
Volume: 70 Issue: 5
First Page: 601 Last Page: 620
ID: 2228471
Publisher Id: 78068095
PubMed Id: 591914

Increased intracellular sodium mimics some but not all aspects of photoreceptor adaptation in the ventral eye of Limulus

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