Circadian behavioral rhythms during various light-intensity cycles in rats

Usui, Setsuo; Takahashi, Yasuro; Honda, Yoshiaki; Ebihara, Shigemitsu

doi:10.1016/0031-9384(89)90030-9

Cited by 17 publications

(8 citation statements)

References 24 publications

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“…Several studies suggested that rhythm‐entraining properties of sinusoidal light intensity cycles might be different from the LD alternation cycles 2 , 5 . The present results also suggest the difference in rhythm‐entraining power between the light intensity cycle and LD alternation.…”

Section: Discussionsupporting

confidence: 62%

“…However, there have been few studies investigating the role of illuminance changes in the entrainment of circadian rhythms. We previously reported that rat circadian rhythms entrained to sinusoidal light intensity cycles with a period of 24 h 2 . In the present study, the period of the sinusoidal light intensity cycles was shortened from 23.5 h to 23 h to assess the lower entrainable limit of rat circadian rhythms.…”

Section: Introductionmentioning

confidence: 81%

“…Light was provided by an incandescent bulb fixed 36 cm above the top of the cage. The light intensity measured at the top of the cage was automatically controlled in 1‐min steps by a programmable illuminance‐controlling system 2 , 3 …”

Section: Methodsmentioning

confidence: 99%

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The lower entrainable limit of rat circadian rhythm to sinusoidal light intensity cycles: A preliminary study

Usui

Okazaki

Takahashi

1999

Psychiatry Clin Neurosci

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The lower entrainable limit of the circadian behavioral rhythm was examined in rats exposed to sinusoidal light intensity cycles with maximum illuminance of 20 lux and the minimum of 0.01 lux. The period (T) of the light intensity cycle was initially kept at 23.5 h for 20 cycles, and then shortened to 23 h for 33 cycles. Thereafter the rats were released into constant darkness. Five out of 10 rats entrained their circadian rhythms to T = 23.5-h cycle, and they also entrained to the T = 23-h cycle. The phase angle of entrainment was almost unchanged when T was shortened from 23.5 h to 23 h. These results suggest that the T = 23-h cycle was close to the lower limit of entrainment.

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Section: Discussionsupporting

confidence: 62%

Section: Introductionmentioning

confidence: 81%

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The lower entrainable limit of rat circadian rhythm to sinusoidal light intensity cycles: A preliminary study

Usui

Okazaki

Takahashi

1999

Psychiatry Clin Neurosci

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“…Thus, dim red light may act similar on the circadian pacemaker as dim white light. Our study confirms previous findings that red light is a Zeitgeber in rodents (Dunn et al, 1972, McCormack and Sontag, 1980, Wald and Grown, 1956, Usui et al, 1989, Zervanos and Davis, 1968. Although no histological evidence was obtained or special measurements were made to establish the amount of damage to the photoreceptors, we might assume considerable destruction.…”

Section: Conclusion and Discussionsupporting

confidence: 91%

Cycles of dim red light capable of entraining circadian rhythms of rats after long‐term exposure to constant white light

Ruis

Rietveld

1992

Journal of Interdisiplinary Cycle Research

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In circadian studies dim red light is often used as a convenient alternative for darkness because it would not affect the pacemaking system. In this study male Wistar rats were first exposed to constant light (LL) for 3 months and next to LD 14:10 cycles of dim red light (> 610 nm; 1 -5 μWatt/cm 2 ) while recording feeding behaviour. All rats displayed entrainment of the circadian feeding rhythm to the red light cycle. A phase reversal of the LD cycle was followed by a gradual reentrainment over 5-8 weeks via delaying transients.It was concluded that dim red light acts as a weak Zeitgeber and that cone-like photoreceptor surviving long-term LL exposure could mediate entrainment.

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“…This feedback system enabled us to avoid unexpected illuminance changes caused by occasional voltage changes of the alternating current source or by aging of the light bulb. Details regarding this system have been reported previously (20,22).…”

Section: Light Intensity Controlmentioning

confidence: 99%

Range of entrainment of rat circadian rhythms to sinusoidal light-intensity cycles

Usui

Takahashi

Okazaki

2000

American Journal of Physiology-Regulatory, Integrative and Comp

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The range of entrainment of the circadian behavioral rhythm was compared between two groups of Sprague-Dawley rats (each n = 10) exposed to daily cycles of rectangular light-dark alternation (LD) and sinusoidal fluctuations of light intensity (SINE), respectively. The maximum illuminance (20 lx), the minimum illuminance (0.01 lx), and the total amount of light exposure per cycle were the same under the two lighting conditions. The periods (Ts) of both lighting cycles were lengthened stepwise from 24 through 25, 26, 26.5, 27, 27. 5, and 28 h to 28.5 h in experiment 1 and were shortened stepwise from 24 through 23.5, 23, and 22.5 h to 22 h in experiment 2. Each T cycle lasted for 30 cycles. In experiment 1, 60% of rats under the LD condition entrained up to T = 28.5 h, whereas 50% of rats under the SINE condition entrained up to T = 28.5 h. In experiment 2, no animal under the LD condition entrained to T < 23.5 h, whereas 40% of rats under the SINE condition entrained down to T = 23 h and 20% of rats remained to entrain down to T = 22 h cycles. The phase angle of entrainment was systematically changed, depending on T under both conditions. These results suggest that the lower limit of entrainment is expanded under the SINE condition compared with the LD condition.

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Circadian behavioral rhythms during various light-intensity cycles in rats

Cited by 17 publications

References 24 publications

The lower entrainable limit of rat circadian rhythm to sinusoidal light intensity cycles: A preliminary study

The lower entrainable limit of rat circadian rhythm to sinusoidal light intensity cycles: A preliminary study

Cycles of dim red light capable of entraining circadian rhythms of rats after long‐term exposure to constant white light

Range of entrainment of rat circadian rhythms to sinusoidal light-intensity cycles

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