Entrainment of the female hamster to reversed photoperiod: Role of the pineal☆

Finkelstein, Joel S.; Baum, Frank R.; Campbell, Constance S.

doi:10.1016/0031-9384(78)90283-4

Cited by 71 publications

(28 citation statements)

References 32 publications

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“…In humans, melatonin may be effective in alleviating jet lag, improving sleep quality and speeding up the resynchronisation of plasma melatonin and cortisol rhythms (Arendt et al 1986(Arendt et al , 1987. Not only melatonin given at a certain time of day but also pinealectomy (Quay 1970(Quay , 1972Kincl et al 1970;Finkelstein et al 1978) and intrahypothalamic melatonin implants (Murakami et al 1983) may speed up the resynchronisation of the circadian system. The presence or absence of melatonin at a certain phase may apparently play a role in the reentrainment mechanism.…”

Section: Discussionmentioning

confidence: 99%

Melatonin accelerates reentrainment of the circadian rhythm of its own production after an 8-h advance of the light-dark cycle

1989

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The rhythm in melatonin production in the rat is driven by a circadian rhythm in the pineal N-acetyltransferase (NAT) activity. Rats adapted to an artificial lighting regime of 12 h of light and 12 h of darkness per day were exposed to an 8-h advance of the light-dark regime accomplished by the shortening of one dark period; the effect of melatonin, triazolam and fluoxetine, together with 5-hydroxytryptophan, on the reentrainment of the NAT rhythm was studied. In control rats, the NAT rhythm was abolished during the first 3 cycles following the advance shift. It reappeared during the 4th cycle; however, the phase relationship between the evening rise in activity and the morning decline was still compressed. Melatonin accelerated the NAT rhythm reentrainment. In rats treated chronically with melatonin at the new dark onset, the rhythm had already reappeared during the 3rd cycle, in the middle of the advanced night, and during the 4th cycle, the phase relationship between the evening onset and the morning decline of the NAT activity was the same as before the advance shift. In rats treated chronically with melatonin at the old dark onset or in those treated with melatonin 8 h, 5 h and 2 h after the new dark onset during the 1st, 2nd and 3rd cycle, respectively, following the advance shift, the NAT rhythm reappeared during the 3rd cycle as well but in the last third of the advanced night only. Neither triazolam nor fluoxetine together with 5-hydroxytryptophan administered around the new dark onset facilitated NAT rhythm reentrainment after the 8-h advance of the light-dark cycle.

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Section: Discussionmentioning

confidence: 99%

Melatonin accelerates reentrainment of the circadian rhythm of its own production after an 8-h advance of the light-dark cycle

1989

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“…While pinealectomy itself did not affect behavioral circadian rhythms [29], these animals entrained to a reversed lighting cycle more rapidly than those with the pineal system intact [7,30]. As light is the most potent entraining signal known, it is surprising that the efficacy of light increases in the absence of circulating melatonin.…”

Section: Effects Of Altered Peripheral Melatonin Profiles On Circadiamentioning

confidence: 91%

Circadian actions of melatonin at the suprachiasmatic nucleus

Gillette

McArthur

1995

Behavioural Brain Research

110

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The biological clock in the suprachiasmatic nucleus (SCN) of the hypothalamus plays a well-defined role in regulating melatonin production by the pineal. Emerging evidence indicates that melatonin itself can feed back upon the SCN and thereby influence circadian functions. Melatonin administration has been shown to entrain activity rhythms in rodents and humans. Melatonin binds specifically within the SCN and alters SCN physiology by both acute and clock-resetting mechanisms. The circadian clock in the SCN appears to temporally restrict its own sensitivity to melatonin, such that physiological sensitivity is greatest in the subjective dusk period

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“…At present, there is a controversy as to whether melatonin affects the mammalian circadian rhythmicity. Perhaps the strongest evidence for a melatonin effect on circadian func tion comes from the observation that rats [28] and hamsters [14] re-entrain faster to a changed light:dark cycle if they are pinealectomized. Furthermore, Redman et al [29] re ported an entraining effect of daily melatonin injections in rats under constant darkness.…”

Section: Discussionmentioning

confidence: 99%

Daily Melatonin Injections Affect the Expression of Circadian Rhythmicity in Djungarian Hamsters Kept under a Long-Day Photoperiod

Puchalski¹,

Gr²

1988

Neuroendocrinology

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Djungarian hamsters (Phodopus sungorus) kept under a long-day photoperiod (16 h light :8 h dark) were injected with melatonin each day. Hamsters which responded physiologically to this treatment (gonadal regression, molt, body weight loss) phase-advanced onset and extended duration of activity. Hamsters which were physiologically insensitive to melatonin injections did not exhibit such changes in activity pattern and often failed to entrain to the light :dark cycle. Hamsters given saline injections did not alter activity or exhibit gonadal regression, weight loss and molt to the winter pelt. Melatonin-sensitive hamsters compressed duration of activity when they became physiologically refractory to the melatonin treatment (weeks 27–29). At the same time, melatonin-insensitive hamsters became entrained to the light :dark cycle. Thus, daily melatonin injections induce short-day-like adjustments in activity under a long-day photoperiod. These changes in activity are correlated with melatonin-induced gonadal regression, weight loss and molt.

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Entrainment of the female hamster to reversed photoperiod: Role of the pineal☆

Cited by 71 publications

References 32 publications

Melatonin accelerates reentrainment of the circadian rhythm of its own production after an 8-h advance of the light-dark cycle

Melatonin accelerates reentrainment of the circadian rhythm of its own production after an 8-h advance of the light-dark cycle

Circadian actions of melatonin at the suprachiasmatic nucleus

Daily Melatonin Injections Affect the Expression of Circadian Rhythmicity in Djungarian Hamsters Kept under a Long-Day Photoperiod

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