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Cellular mechanisms that underlie bleaching and background adaptation.
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MedLine Citation:
PMID:  1698916     Owner:  NLM     Status:  MEDLINE    
Experiments were performed on rod photoreceptors isolated from the eye of the larval tiger salamander to determine if the same or different mechanisms underlie the desensitization produced by dim background light (background adaptation) and that which persists in the steady state in darkness after a significant fraction of the photopigment is bleached (bleaching adaptation). We have examined adaptational effects after light that bleached between approximately 50% and 95% of the photopigment under conditions which preclude pigment regeneration. The steady-state desensitization, far greater than that predicted by quantum-catch loss, is relieved upon regeneration of the visual pigment with 11-cis retinal. We measured the spread of desensitization along the long axis of the rod after a local bright bleach at one end by comparing responses to dim local test flashes elicited in different regions of the outer segment, before and after bleaching. The space constant for this spread was less than 2.5 microns. We have previously measured the space constant for the longitudinal spread of desensitization during a local dim background in Ambystoma rods to be 7 microns. This is similar to a space constant of 6 microns measured under similar conditions in Bufo rods by Lamb et al. (1981. J. Physiol. 319:463-496). If calcium carries the signal for background desensitization, this difference in space constant for background and bleaching adaptation precludes it as the messenger for the steady component of bleaching adaptation. Experiments with isobutylmethyl xanthine (IBMX) also indicate that Ca2+ as well as c-GMP are unlikely regulators of bleaching desensitization, since elevation of cytosolic levels of both of these internal messengers by IBMX has little effect on sensitivity in bleach-adapted cells. All of our findings are consistent with the notion that bleaching adaptation is not mediated by a freely diffusible cytoplasmic messenger.
M C Cornwall; A Fein; E F MacNichol
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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:  96     ISSN:  0022-1295     ISO Abbreviation:  J. Gen. Physiol.     Publication Date:  1990 Aug 
Date Detail:
Created Date:  1990-11-15     Completed Date:  1990-11-15     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  2985110R     Medline TA:  J Gen Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  345-72     Citation Subset:  IM    
Department of Physiology, Boston University School of Medicine, Massachusetts 02118.
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MeSH Terms
1-Methyl-3-isobutylxanthine / pharmacology
Adaptation, Physiological / drug effects,  physiology*
Calcium / pharmacology
Cyclic GMP / metabolism
Larva / cytology,  physiology
Photoreceptor Cells / cytology,  metabolism,  physiology*
Pigmentation / drug effects,  physiology*
Second Messenger Systems / drug effects,  physiology
Time Factors
Grant Support
Reg. No./Substance:
28822-58-4/1-Methyl-3-isobutylxanthine; 7440-70-2/Calcium; 7665-99-8/Cyclic GMP

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: 8 Year: 1990
Volume: 96 Issue: 2
First Page: 345 Last Page: 372
ID: 2228990
Publisher Id: 91011328
PubMed Id: 1698916

Cellular mechanisms that underlie bleaching and background adaptation

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