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The pattern of circadian behavioral rhythms is photoperiod-dependent, highlighted by the conservation of a phase relation between the behavioral rhythm and photoperiod. A model of two separate, but mutually coupled, circadian oscillators has been proposed to explain photoperiodic responses of behavioral rhythm in nocturnal rodents: an evening oscillator,(More)
The circadian rhythms in mammals are regulated by a pacemaker located in the suprachiasmatic nucleus of the hypothalamus. Four clock-gene families have been found to be involved in a transcription-translation feedback loop that generates the circadian rhythm at the intracellular level. The proteins Clock and Bmal1 form a heterodimer which activates the(More)
The ability of nursing mothers to entrain the circadian pacemaker of rat pups was examined by measuring the rat Per1 (rPer1) and rPer2 expression levels in the suprachiasmatic nuclei (SCN). Newborn rats from mothers under a light-dark cycle (LD) were blinded immediately after birth and reared by foster mothers under either LD (LD blind pups) or reversed(More)
In the rat suprachiasmatic nucleus slice culture, circadian rhythms in the release of arginine vasopressin and vasoactive intestinal polypeptide were measured simultaneously and longitudinally. The phase relationship between the two peptide rhythms was relatively constant in the culture without a treatment of antimitotic drugs but became diverse by an(More)
Temporal profiles of the amount of vasoactive intestinal polypeptide (VIP) were examined in the medium of organotypic suprachiasmatic nucleus (SCN) slice cultures over a 2-day period. Arginine-vasopressin (AVP) level was also measured in the same medium. The slices of the SCN were obtained from 7-8-day-old rats and cultured individually in tubes on a roller(More)
Female rats were lesioned in the suprachiasmatic nuclei (SCN) electrolytically and treated with methamphetamine. The SCN lesions abolished the circadian locomotor rhythm completely. When methamphetamine was administered in the drinking water, robust rhythmicities in locomotor activity appeared in the SCN lesioned rats, which did not entrain to the 24 hr(More)
The circadian system in mammals consists of the central clock in the hypothalamic suprachiasmatic nucleus (SCN) and the peripheral clocks in a variety of tissues and organs. The SCN clock entrains to a light-dark cycle and resets the peripheral clocks. In addition, there are at least two other clocks in the circadian domain which are independent of the SCN(More)
Regional specificities of the dorsal and ventral regions of the suprachiasmatic nucleus (SCN) were examined to elucidate the structure of multioscillator circadian organization. The circadian rhythms of arginine vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) release, and of electrical activity of individual neurons were measured in an(More)
The circadian periods of single cultured neurons of the hypothalamic suprachiasmatic nucleus (SCN) in rats were assessed by means of multi-electrode array dish. Although the mean circadian period was not different between the dispersed cell culture and organotypic slice culture, the periods distributed in a wide range from 20.0 to 30.9 h in the former(More)
Phase response curves (PRC) for the spontaneous locomotor rhythm were constructed by applying short light pulses to rats in constant darkness (DD). The offset of locomotor activity as well as the onset was taken as a phase reference (offset PRC vs. onset PRC). The amount of phase shift yielded by light pulses was evaluated on the next day of pulse treatment(More)