Document Detail

Modulation of transduction gain in light adaptation of retinal rods.
MedLine Citation:
PMID:  8011583     Owner:  NLM     Status:  MEDLINE    
The effect of light adaptation on the period of photocurrent saturation induced by a bright stimulating flash was examined in rod photoreceptors of the larval-stage tiger salamander (Ambystoma tigrinum). Using suction electrodes, photocurrent responses to brief flashes were recorded from single, isolated rods in the presence and absence of steady background illumination. Background light decreased the saturation period (T) measured at fixed flash intensity (fixed If) and in this respect light-adapted the saturating response. Effects of the background on responses to weak (i.e. subsaturating) and bright flashes were compared with changes in a parameter, phi = e-delta T/TR*, where delta T is the decrease in saturation period, and where TR* is the slope of the line that relates T and ln If in a given state of adaptation. Dark- and light-adapted responses to flash intensities IDf and ILf, respectively, exhibited similar absolute peak photocurrent and falling-phase kinetics when IDf and ILf satisfied the relation, IDf = phi (ILf + IbTR*), where Ib is the background intensity. It is argued that phi approximates the relative PDE*/R* gain of transduction, i.e. the relative peak level of activated cGMP phosphodiesterase (PDE*) produced by a given, small amount of photoactivated visual pigment (R*). Interpreted on this view, the results imply that light adaptation derives largely from a decrease in PDE*/R gain, rather than from the stimulation of guanylate cyclase activity. The data are consistent with the possibility that modulation of the lifetime of PDE* underlies the background dependence of phi.
D R Pepperberg; J Jin; G J Jones
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Visual neuroscience     Volume:  11     ISSN:  0952-5238     ISO Abbreviation:  Vis. Neurosci.     Publication Date:    1994 Jan-Feb
Date Detail:
Created Date:  1994-07-22     Completed Date:  1994-07-22     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8809466     Medline TA:  Vis Neurosci     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  53-62     Citation Subset:  IM    
Lions of Illinois Eye Research Institute, Department of Ophthalmology and Visual Sciences, University of Illinois, Chicago College of Medicine 60612.
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MeSH Terms
Adaptation, Ocular*
Dark Adaptation
Photic Stimulation
Retinal Rod Photoreceptor Cells / physiology*
Signal Transduction / physiology*
Grant Support

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