@article{PAR00002986,
  title = {{E}ffects of irradiance and stimulus duration on early gene expression ({F}os) in the suprachiasmatic nucleus : temporal summation and reciprocity},
  author = {{D}khissi-{B}enyahya, {O}. and {S}icard, {B}runo and {C}ooper, {H}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he daily behavioral, physiological, and hormonal rhythms in mammals are regulated by an endogenous circadian clock located in the suprachiasmatic nucleus ({SCN}) and are synchronized by the natural 24 hr light/dark cycle. {W}e studied the response properties (threshold, saturation, and linearity) of the photic system to irradiance by assaying light induction of {F}os, the protein product of the immediate early gene c-fos. {F}os expression was quantified by image analysis in the {SCN} and in the retina. {F}os expression in the {SCN} and retina are unrelated because the response differs in terms of threshold, saturation, and range. {I}n the {SCN}, {F}os expression increases proportionately to increases in both irradiance and duration of light exposure. {T}he photic system shows a linear temporal integration of photons for durations ranging from 3 sec to 47.5 min. {T}he principal result of this study shows that in the {SCN}, {F}os expression is directly proportional to the total number of photons rather than to irradiance or duration alone (reciprocity), and that integration occurs over a range of 5 log units of photon number. {T}his report provides the first demonstration that the mechanism of photon integration by the circadian system is expressed at a cellular level in the {SCN}.},
  keywords = {},
  booktitle = {},
  journal = {{J}ournal of {N}euroscience},
  volume = {20},
  numero = {20},
  pages = {7790--7797},
  year = {2000},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00002986},
}