Accelerated re-entrainment to advanced light cycles in BALB/cJ mice

Abstract

Circadian rhythms in mammals are coordinated by the suprachiasmatic nuclei (SCN) of the hypothalamus, which are most potently synchronized to environmental light-dark cycles. Large advances in the light-dark cycle typically yield gradual advances in activity rhythms on the order of 1-2 hours per day until re-entrainment is complete due to limitations on the circadian system which are not yet understood. In humans, this delay until re-entrainment is accomplished is experienced as jetlag, with accompanying symptoms of malaise, decreased cognitive performance, sleep problems and gastrointestinal distress. In these experiments, locomotor rhythms of BALB/cJ mice monitored by running wheels were shown to re-entrain to large 6 or 8-hour shifts of the light-dark cycle within 1-2 days, as opposed to the 5-7 days required for C57BL/6J mice. A single-day 6-hr advance of the LD cycle followed by release to constant darkness yielded similar phase shifts, demonstrating that exaggerated re-entrainment is not explained by masking of activity by the light-dark cycle. Responses in BALB/cJ mice were similar when monitored instead by motion detectors, indicating that wheelrunning exercise does not influence the magnitude of responses. Neither brief (15 min) light exposure late during subjective nighttime nor 6-hr delays of the light-dark cycle produced exaggerated locomotor phase shifts, indicating that BALB/cJ mice do not merely experience enhanced sensitivity to light. Fos protein was expressed in cells of the SCN following acute light exposure at ZT10 of their previous light-dark cycle, a normally non-responsive time in the circadian cycle, but only in BALB/cJ (and not C57BL/6J) mice that had been subjected two days earlier to a single-day 6-hr advance of the light-dark cycle, indicating that their SCN had been advanced by that treatment. BALB/cJ mice may thus serve as a useful comparative model for studying molecular and physiological processes that limit responsiveness of circadian clocks to photic input.

Rapid Jetlag Resetting of Behavioral, Physiological, and Molecular Rhythms in Proestrous Female Mice

“…*p < 0.05. female mice, which lasts about 7 days. Such transient shift of behavioral rhythms to a new LD cycle has already been well characterized in male mice and it has been shown that adaptation is a gradual process and requires multiple transient circadian cycles of 5 to 7 days following a 6-to 8-h phase advance of the LD cycle (Honma et al, 1985;Legates et al, 2009).…”

Epigenomics: maternal high‐fat diet exposure in utero disrupts peripheral circadian gene expression in nonhuman primates

“…Specifically, when Npas2 expression is low, Per2 and Rev-erb-␣ expression will be high because of the feedback inhibitory mechanism of circadian gene expression. Traditionally, in most animal models of circadian gene expression, animals will be sacrificed at specific time points to determine the phase of gene expression levels over a 24-h period (47)(48)(49)(50). However, in our primate model, this is not technically feasible.…”

Rapid Response and Slow Recovery of the H3K4me3 Epigenomic Marker in the Liver after Light-mediated Phase Advances of the Circadian Clock

“…We therefore asked whether the liver circadian epigenome would reentrain to the light-dark cycle after a week (Recovery Group), a time point shown by others (LeGates et al, 2009; Kiessling et al, 2010; Summa et al, 2012) to be sufficient for behavioral reentrainment, as defined by locomotor activity rhythms. We verified in identical conditions that locomotor activity reentrains within a week after a 6-h phase advance (Fig.…”