Mistimed restricted feeding disrupts circadian rhythms of male mating behavior and female preovulatory LH surges in mice.

In rodents, eating at atypical circadian times, such as during the biological rest phase when feeding is normally minimal, reduces fertility. Prior findings suggest this fertility impairment is due, at least in part, to reduced mating success. However, the physiological and behavioral mechanisms underlying this reproductive suppression are not known.

Female fertility does not require in suprachiasmatic nucleus neurons expressing arginine vasopressin, vasoactive intestinal peptide, or neuromedin-S.

Disruptions to the circadian system alter reproductive capacity, particularly in females. Mice lacking the core circadian clock gene, , are infertile and have evidence of neuroendocrine disruption including the absence of the preovulatory luteinizing hormone (LH) surge and enhanced responsiveness to exogenous kisspeptin. Here, we explore the role of in suprachiasmatic nucleus (SCN) neuron populations known to project to the neuroendocrine axis.

Naturalistic Intensities of Light at Night: A Review of the Potent Effects of Very Dim Light on Circadian Responses and Considerations for Translational Research.

In this review, we discuss the remarkable potency and potential applications of a form of light that is often overlooked in a circadian context: naturalistic levels of dim light at night (nLAN), equivalent to intensities produced by the moon and stars. It is often assumed that such low levels of light do not produce circadian responses typically associated with brighter light levels. A solid understanding of the impacts of very low light levels is complicated further by the broad use of the somewhat ambiguous term "dim light," which has been used to describe light levels ranging seven orders of magnitude.

Circadian Profile of an Emergency Medicine Department: Scheduling Practices and Their Effects on Sleep and Performance.

Background: Shiftwork causes circadian disruption and is the primary reason for attrition from Emergency Medicine.

Objectives: We aimed to develop concrete recommendations to mitigate negative effects of shiftwork based on measures of work, sleep, alertness, and performance in emergency physicians.

Methods: Thirty-one Emergency Medicine residents were surveyed retrospectively about sleep and alertness on different shifts.

Enhanced Circadian Entrainment in Mice and Its Utility under Human Shiftwork Schedules.

The circadian system is generally considered to be incapable of adjusting to rapid changes in sleep/work demands. In shiftworkers this leads to chronic circadian disruption and sleep loss, which together predict underperformance at work and negative health consequences. Two distinct experimental protocols have been proposed to increase circadian flexibility in rodents using dim light at night: rhythm bifurcation and T-cycle (i.

Physiological, behavioral and environmental factors influence bifurcated circadian entrainment in mice.

Under permissive conditions, mice and hamsters exposed to a polyphasic light regime consisting of two light and two dark phases every 24 h (Light:Dark:Light:Dark; LDLD) can adopt a bifurcated entrainment pattern with roughly equal amounts of running wheel activity in each of the two nights. This rhythm "bifurcation" has significant after-effects on increased circadian adaptability: Mice that have been bifurcated show accelerated rates of re-entrainment after a sudden phase shift and have a markedly expanded range of entrainment. Identifying environmental and physiological factors that facilitate or prevent rhythm bifurcation in LDLD conditions will contribute to an understanding of mechanisms underlying enhanced circadian plasticity.

Simple Lighting Manipulations Facilitate Behavioral Entrainment of Mice to 18-h Days.

In an invariantly rhythmic world, a robust and stable mammalian circadian clock is presumed to confer fitness advantages. In shift-work or after rapid transmeridian travel, however, a stable clock might be maladaptive and a more flexibly resettable clock may have advantages. The rate at which rodents can adjust to simulated time zone travel and the range of entrainment can be markedly increased through simple light manipulations, namely, by exposing animals to extremely dim light (<0.

Extraordinary behavioral entrainment following circadian rhythm bifurcation in mice.

The mammalian circadian timing system uses light to synchronize endogenously generated rhythms with the environmental day. Entrainment to schedules that deviate significantly from 24 h (T24) has been viewed as unlikely because the circadian pacemaker appears capable only of small, incremental responses to brief light exposures. Challenging this view, we demonstrate that simple manipulations of light alone induce extreme plasticity in the circadian system of mice.

Short Blue Light Pulses (30 Min) in the Morning Support a Sleep-Advancing Protocol in a Home Setting.

Many people in our modern civilized society sleep later on free days compared to work days. This discrepancy in sleep timing will lead to so-called 'social jetlag' on work days with negative consequences for performance and health. Light therapy in the morning is often proposed as the most effective method to advance the circadian rhythm and sleep phase.