Document Detail


Fast-acting compressive and facilitatory nonlinearities in light-adapted fly photoreceptors.
MedLine Citation:
PMID:  7762884     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Light-adapted fly photoreceptor cells were stimulated with brief positive and negative contrast flashes (contrast = delta I/I, I = intensity). Membrane potential responses to a wide range of flash intensities were well-fitted by a static nonlinearity followed by a compartmental model represented by a gamma function. However, the agreement improved if one parameter of the gamma function, n, varied quadratically with input light intensity. Response amplitude and time to peak were estimated from the fitted parameters. Response amplitude varied approximately linearly with contrast but showed nonlinear compression with the largest negative flashes. Reducing the background light level by 3 decades or hyperpolarizing the cell electrically produced stronger nonlinear compression with both contrast polarities. This is probably due to fast voltage-activated K+ channels. Responses to double flashes with varying time separations were well-fitted by summed gamma functions, allowing separation of the individual flash responses. There was no detectable time-dependent interaction between paired positive flashes at all separations. However, the response to two negative flashes was greater than the linear prediction at short separations, and this facilitatory nonlinearity decayed with a time constant of about 1 msec. The facilitation is probably related to resonant behavior in light-adapted photoreceptors and may be due to an IP3-induced intracellular Ca2+ release.
Authors:
M Weckström; M Juusola; R O Uusitalo; A S French
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Annals of biomedical engineering     Volume:  23     ISSN:  0090-6964     ISO Abbreviation:  Ann Biomed Eng     Publication Date:    1995 Jan-Feb
Date Detail:
Created Date:  1995-06-29     Completed Date:  1995-06-29     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0361512     Medline TA:  Ann Biomed Eng     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  70-7     Citation Subset:  IM    
Affiliation:
Department of Physiology, University of Oulu, Finland.
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MeSH Terms
Descriptor/Qualifier:
Animals
Calcium-Transporting ATPases
Dark Adaptation / physiology*
Diptera / physiology*
Evaluation Studies as Topic
Linear Models
Membrane Potentials
Models, Biological
Models, Statistical
Photoreceptor Cells, Invertebrate / physiology*
Reaction Time
Time Factors
Chemical
Reg. No./Substance:
EC 3.6.1.8/Calcium-Transporting ATPases

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


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