Premium
Temperature dependence of the light response in rat rods.
Author(s) -
Robinson D W,
Ratto G M,
Lagnado L,
McNaughton P A
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019564
Subject(s) - amplitude , q10 , light intensity , photoisomerization , chemistry , temperature coefficient , phase (matter) , time constant , analytical chemistry (journal) , materials science , optics , physics , isomerization , chromatography , biochemistry , respiration , botany , organic chemistry , electrical engineering , composite material , biology , engineering , catalysis
1. The effects of temperature on the light responses of rat rods have been investigated over the range 17‐40 degrees C. 2. The amplitude of the light‐sensitive current increased with temperature with a mean temperature coefficient (Q10) of 2.47. 3. The amplitude of the Na(+)‐Ca2+, K+ exchange current decreased with temperature when expressed as a fraction of the light‐sensitive current, showing that the light‐sensitive channel becomes less permeable to calcium as the temperature is raised. The time constant of relaxation of the exchange current was little affected by temperature. 4. The flash intensity required to give a half‐saturating response increased with temperature with a mean Q10 of 1.68. 5. The responses to single photoisomerizations were determined from amplitude histograms of the responses to dim‐flash trains. The amplitude of the response to a single photoisomerization decreased with temperature when expressed as a fraction of the light‐sensitive current, but the change was not sufficient to account for the overall decrease in sensitivity. 6. The fraction of dim flashes that produced a photoisomerization decreased with temperature. This decrease in photon capture efficiency together with the decrease in the relative size of the single photon event fully accounts for the observed change in sensitivity. 7. The speed of the falling phase of the dim‐flash response was accelerated more by warming than the rising phase, and it was therefore not possible to superimpose light responses at different temperatures by a simple change in time scale.