| Human retinal light sensitivity and melatonin rhythms following four days in near darkness. | |
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MedLine Citation:
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PMID: 19142760 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The rods in the retina are responsible for night vision, whereas the cone system enables day vision. We studied whether rod function in humans exhibits an endogenous circadian rhythm and if changes occur in conditions of prolonged darkness. Seven healthy subjects (mean age+/-SD: 25.6+/-12.3 yr) completed a 4.5-day protocol during which they were kept in complete darkness (days 1 and 4) and near darkness (<0.1 lux red light, days 2 and 3). Electroretinography (ERG) and saliva collections were done at intervals of at least 3 h for 27 h on days 1 and 4. Full-field ERGs were recorded over 10 low-intensity green light flashes known to test predominantly rod function. As a circadian marker, salivary melatonin concentration was measured by radioimmunoassay. The ERG data showed that rod responsiveness to light progressively diminished in darkness (significantly lower a- and b-wave amplitudes, longer b-wave implicit time). The decrease in amplitude (b-wave) from day 1 to day 4 averaged 22+/-14%. After correction for the darkness-related linear trend, the circadian variations in ERG indices were weak and usually non-significant, with slightly higher responsiveness to light during the day than night. Rod sensitivity (by K index) tended to decrease. Strikingly, the overall amount of melatonin secretion (area under 24 h curve) also decreased from day 1 to day 4 by 33.1+/-18.9% (p=.017). The drift of the melatonin rhythm phase was within the normal range, less than 56 min over three days. There was no significant correlation between the changes in ERG responses and melatonin. In conclusion, scotopic retinal response to (low-intensity) light and the amount of melatonin secreted are diminished when humans are kept in continuous darkness. Both processes may have a common underlying mechanism implicating a variety of neurochemicals known to be involved in the regulation of both photoreceptor and pineal gland function. |
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Authors:
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Konstantin V Danilenko; Igor L Plisov; Anna Wirz-Justice; Marc Hebert |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Chronobiology international Volume: 26 ISSN: 1525-6073 ISO Abbreviation: Chronobiol. Int. Publication Date: 2009 Jan |
Date Detail:
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Created Date: 2009-01-14 Completed Date: 2009-03-10 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8501362 Medline TA: Chronobiol Int Country: United States |
Other Details:
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Languages: eng Pagination: 93-107 Citation Subset: IM |
Affiliation:
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Institute of Internal Medicine, Siberian Branch of the Russian Academy of Medical Sciences, Novosibirsk, Russia. dani@irs.ru |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Circadian Rhythm* Color Darkness* Electroretinography Female Humans Melatonin / analysis, secretion* Middle Aged Retinal Rod Photoreceptor Cells / physiology* Saliva / chemistry Time Factors Young Adult |
| Chemical | |
Reg. No./Substance:
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73-31-4/Melatonin |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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