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Pressure injection of calcium both excites and adapts Limulus ventral photoreceptors.
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MedLine Citation:
PMID:  3734748     Owner:  NLM     Status:  MEDLINE    
Single pressure injections of 1-2 mM calcium aspartate into the light-sensitive region of Limulus ventral photoreceptors resulted in a rapid, 20-40-mV depolarization lasting approximately 2 s. The depolarization closely followed the rise in intracellular free calcium caused by the injection, as indicated by aequorin luminescence. The depolarization was followed by reversible desensitization (adaptation) of responses to both light and inositol 1,4,5 trisphosphate. Similar single injections of calcium into the light-insensitive region of the receptor were essentially without effect, even though aequorin luminescence indicated a large, rapid rise in intracellular free calcium. The depolarization caused by injection of calcium arose from the activation of an inward current with rectification characteristics and a reversal potential between +10 and +20 mV that were similar to those of the light-activated conductance, which suggests that the same channels were activated by light and by calcium. The reversal potentials of the light- and calcium-activated currents shifted similarly when three-fourths of the extracellular sodium was replaced by sucrose, but were not affected by a similar replacement of sodium by lithium. The current activated by calcium was abolished by prior injection of a calcium buffer solution containing EGTA. The responses of the same cells to brief light flashes were slowed and diminished in amplitude, but were not abolished after the injection of calcium buffer. Light adaptation and prior injection of calcium diminished the calcium-activated current much less than they diminished the light-activated current.
R Payne; D W Corson; A Fein
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of general physiology     Volume:  88     ISSN:  0022-1295     ISO Abbreviation:  J. Gen. Physiol.     Publication Date:  1986 Jul 
Date Detail:
Created Date:  1986-09-17     Completed Date:  1986-09-17     Revised Date:  2010-09-10    
Medline Journal Info:
Nlm Unique ID:  2985110R     Medline TA:  J Gen Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  107-26     Citation Subset:  IM    
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MeSH Terms
Adaptation, Physiological / drug effects
Barium / pharmacology
Calcium / administration & dosage*,  pharmacology
Electric Conductivity
Horseshoe Crabs
Injections / methods
Luminescent Measurements
Magnesium / pharmacology
Photoreceptor Cells / drug effects*
Sodium / pharmacology
Strontium / pharmacology
Grant Support
Reg. No./Substance:
50934-79-7/Aequorin; 7439-95-4/Magnesium; 7440-23-5/Sodium; 7440-24-6/Strontium; 7440-39-3/Barium; 7440-70-2/Calcium

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

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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: 7 Year: 1986
Volume: 88 Issue: 1
First Page: 107 Last Page: 126
ID: 2228784
Publisher Id: 86280337
PubMed Id: 3734748

Pressure injection of calcium both excites and adapts Limulus ventral photoreceptors

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