Figueiro, Bullough, Parsons and Rea (2005) Preliminary evidence for a change in spectral sensitivity of the circadian system at night.

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Preliminary evidence for a change in spectral sensitivity of the circadian system at night.

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CONTRIBUTORS:

	Author:	Figueiro, MG (Rensselaer Polytechnic Institute)
	Author:	Bullough, JD (Rensselaer Polytechnic Institute)
	Author:	Parsons, RH
	Author:	Rea, MS (Rensselaer Polytechnic Institute)

JOURNAL:

Journal of Circadian Rhythms, 3(14), ?? - ??.

YEAR:

2005

PUB TYPE:

Journal Article

SUBJECT(S):

Circadian Rhythms

DISCIPLINE:

No discipline assigned

HTTP:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16336697&query_hl=3&itool=pubmed_docsum

LANGUAGE:

English

PUB ID:

103-424-169 (Last edited on 2006/02/12 14:42:35 US/Mountain)

SPONSOR(S):

ABSTRACT:
BACKGROUND : It is well established that the absolute sensitivity of the suprachiasmatic nucleus to photic stimulation received through the retino-hypothalamic tract changes throughout the 24-hour day. It is also believed that a combination of classical photoreceptors (rods and cones) and melanopsin-containing retinal ganglion cells participate in circadian phototransduction, with a spectral sensitivity peaking between 440 and 500 nm. It is still unknown, however, whether the spectral sensitivity of the circadian system also changes throughout the solar day. Reported here is a new study that was designed to determine whether the spectral sensitivity of the circadian retinal phototransduction mechanism, measured through melatonin suppression and iris constriction, varies at night. METHODS : Human adult males were exposed to a high-pressure mercury lamp [450 lux (170 muW/cm2) at the cornea] and an array of blue light emitting diodes [18 lux (29 muW/cm2) at the cornea] during two nighttime experimental sessions. Both melatonin suppression and iris constriction were measured during and after a one-hour light exposure just after midnight and just before dawn. RESULTS : An increase in the percentage of melatonin suppression and an increase in pupil constriction for the mercury source relative to the blue light source at night were found, suggesting a temporal change in the contribution of photoreceptor mechanisms leading to melatonin suppression and, possibly, iris constriction by light in humans. CONCLUSION : The preliminary data presented here suggest a change in the spectral sensitivity of circadian phototransduction mechanisms at two different times of the night. These findings are hypothesized to be the result of a change in the sensitivity of the melanopsin-expressing retinal ganglion cells to light during the night

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