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Functional decoupling of melatonin suppression and circadian phase resetting in humans

Rahman, Shadab A., St Hilaire, Melissa A., Gronfier, Claude, Chang, Anne-Marie, Santhi, Nayantara, Czeisler, Charles A., Klerman, Elizabeth B. and Lockley, Steven W. (2018) Functional decoupling of melatonin suppression and circadian phase resetting in humans The Journal of Physiology, 596 (11). pp. 2147-2157.

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Continuous experimental light exposures show that, in general, the conditions that produce greater melatonin suppression also produce greater phase shift, leading to the assumption that one can be used as a proxy for the other. We tested this association in 16 healthy individuals who participated in a 9‐day inpatient protocol by assessing melatonin suppression and phase resetting in response to a nocturnal light exposure (LE) of different patterns: (i) dim‐light control (<3 lux; n = 6) or (ii) two 12‐min intermittent bright light pulses (IBL) separated by 36 min of darkness (∼9500 lux; n = 10). We compared these results with historical data from additional LE patterns: (i) dim‐light control (<3 lux; n = 11); (ii) single continuous bright light exposure of 12 min (n = 9), 1.0 h (n = 10) or 6.5 h (n = 6); or (iii) an IBL light pattern consisting of six 15‐min pulses with 1.0 h dim‐light recovery intervals between them during a total of 6.5 h (n = 7). All light exposure groups had significantly greater phase‐delay shifts than the dim‐light control condition (P < 0.0001). While a monotonic association between melatonin suppression and circadian phase shift was observed, intermittent exposure patterns showed significant phase shifts with disproportionately less melatonin suppression. Each and every IBL stimulus induced a similar degree of melatonin suppression, but did not appear to cause an equal magnitude of phase shift. These results suggest unique specificities in how light‐induced phase shifts and melatonin suppression are mediated such that one cannot be used as a proxy measure of the other.

Item Type: Article
Divisions : Faculty of Health and Medical Sciences > School of Biosciences and Medicine
Authors :
Rahman, Shadab A.
St Hilaire, Melissa A.
Gronfier, Claude
Chang, Anne-Marie
Czeisler, Charles A.
Klerman, Elizabeth B.
Lockley, Steven W.
Date : 29 April 2018
DOI : 10.1113/JP275501
Copyright Disclaimer : © 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.
Uncontrolled Keywords : Melatonin; Phase shift; Light
Depositing User : Clive Harris
Date Deposited : 30 Aug 2018 10:30
Last Modified : 17 Jun 2020 05:07

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