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Circadian rhythm bifurcation induces flexible phase resetting by reducing circadian amplitude
Author(s) -
Noguchi Takako,
Harrison Elizabeth M.,
Sun Jonathan,
May Deborah,
Ng Alan,
Welsh David K.,
Gorman Michael R.
Publication year - 2020
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.14086
Subject(s) - circadian rhythm , suprachiasmatic nucleus , clock , light effects on circadian rhythm , biology , medicine , circadian clock , endocrinology , rhythm , entrainment (biomusicology) , per2 , bioluminescence , neuroscience , ecology
Shift‐work and jet‐lag–related disorders are caused by the limited flexibility of the suprachiasmatic nucleus ( SCN ), a master circadian clock in the hypothalamus, to adjust to new light–dark ( LD ) cycles. Recent findings confirmed here establish that behavioral jet lag after simulated time‐zone travel is virtually eliminated following bifurcated circadian entrainment under a novel and atypical 24‐h light:dark:light:dark ( LDLD ) cycle. To investigate the mechanisms of this fast resetting, we examined the oscillatory stability of the SCN and peripheral tissues in LDLD ‐bifurcated mice employing the dissection procedure as a perturbing resetting stimulus. SCN , lung, liver, and adrenal tissue were extracted at times throughout the day from female and male PER 2::Luciferase knock‐in mice entrained to either LDLD or a normal LD cycle. Except for adrenals, the phase of the cultured explants was more strongly set by dissection under LDLD than under normal LD . Acute bioluminescence levels of SCN explants indicate that the rhythm amplitude of PER 2 is reduced and phase is altered in LDLD . Real‐time quantitative PCR suggests that amplitude and rhythmicity of canonical clock genes in the lung, liver, and kidney are also significantly reduced in LDLD in vivo. Furthermore, spatiotemporal patterns of PER 2 peak time in cultured SCN were altered in LDLD . These results suggest that altered gene expression patterns in the SCN caused by bifurcation likely result in fast resetting of behavior and cultured explants, consistent with previously reported mathematical models. Thus, non‐invasive, simple light manipulations can make circadian rhythms more adaptable to abrupt shifts in the environmental LD cycle.