Circadian rhythms, generated in the suprachiasmatic nucleus (SCN), are synchronized to the ambient light/dark (LD) cycle. Long-term disruptions in circadian rhythms are associated with many health problems. However, the underlying mechanisms for such pathologies are not well understood. In the present study, we utilized a chronic jet lag paradigm consisting of weekly 6 h phase shifts in the LD ...

In a previous study we reported that a low daily p.o. dose of cadmium (Cd) disrupted the circadian expression of clock and redox enzyme genes in rat medial basal hypothalamus (MBH). To assess whether melatonin could counteract Cd activity, male Wistar rats (45 days of age) received CdCl(2) (5 ppm) and melatonin (3 μg/mL) or vehicle (0.015% ethanol) in drinking water. Groups of animals receiving...

PURPOSE Melatonin synthesis in mammalian retinal photoreceptors is under photic and circadian control and regulated by changes in the activity of arylalkylamine N-acetyltransferase (AANAT). Recent studies have suggested that retinal dopaminergic neurons contain a circadian pacemaker, and dopamine is the neurotransmitter that drives circadian rhythmicity in the mammalian retina. METHODS To inv...

Many individuals may view stress as an emotion experienced by many; I, myself, was once one of those individuals. In actuality, stress is also a response composed of a series of complex events beginning with the hypothalamo-pituitary-adrenal (HPA) axis. It turns out that components of the HPA axis can be altered by input from hypothalamic nuclei such as the suprachiasmatic nucleus, SCN, and the...

In mammals, the circadian oscillator within the suprachiasmatic nuclei (SCN) entrains circadian clocks in numerous peripheral tissues. Central and peripheral clocks share a molecular core clock mechanism governing daily time measurement. In the rat SCN, the molecular clockwork develops gradually during postnatal ontogenesis. The aim of the present work was to elucidate when during ontogenesis t...

A fundamental property of circadian clocks is that they entrain to environmental cues. The circadian genes, Period1 and Period2, are involved in entrainment of the mammalian circadian system. To investigate the roles of the Period genes in photic entrainment, we constructed phase response curves (PRC) to light pulses for C57BL/6J wild-type, Per1(-/-), Per2(-/-), and Per3(-/-) mice and tested wh...

Shift work has been suggested to be associated with breast cancer risk, and circadian disruption in shift workers is hypothesized as one of the mechanisms of increased cancer risk. There is, however, insufficient molecular evidence supporting this hypothesis. Using the quantitative methodology of pyrosequencing, epigenetic changes in 5-methyl cytosine (5mC) in five circadian genes CLOCK, BMAL1,...

Nursing in the rabbit is under circadian control, and pups have a daily anticipatory behavioral arousal synchronized to this unique event, but it is not known which signal is the main entraining cue. In the present study, we hypothesized that food is the main entraining signal. Using mother-deprived pups, we tested the effects of artificial feeding on the synchronization of locomotor behavior, ...