Interruption of nocturnal pineal melatonin synthesis in spontaneous recrudescent Djungarian hamsters (<i>Phodopus sungorus</i>)

Lerchl, Alexander; Nieschlag, Eberhard

doi:10.1111/j.1600-079x.1992.tb00052.x

Cited by 15 publications

(6 citation statements)

References 29 publications

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“…The observation that the weights of both the ovaries and the uteri did not reach the long-day control values after 38 weeks under 8L:16D ( fig. 3) compares well with the situation recently described for males [20], Like in fe males, the gonads' weights were considerably lower after prolonged exposure to short-day photoperiods as compared to long-day controls. The reason for these ef fects is not yet known.…”

Section: Discussionsupporting

confidence: 89%

“…A possible explanation could be that the animals do not completely 'ignore' the re gressive effects of short-day photoperiods after pro longed exposure to such lighting regimens. The time courses of the physiological events, in the female Djungarian hamster, also compare well to those described in the males [15,20]. The female and male Djungarian hamster seem to be similar in regard to both the shortday induced transition to the winter status and in the sponaneous recrudescence, suggesting a common mech anism of photoperiodic control of reproduction in Phodopus sungorus.…”

Section: Discussionsupporting

confidence: 64%

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Influence of Photoperiod on Pineal Melatonin Synthesis, Fur Color, Body Weight, and Reproductive Function in the Female Djungarian Hamster, Phodopus sungorus

Lerchl¹,

Schlatt²

1993

Neuroendocrinology

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In order to investigate female Djungarian hamsters’ reactions to changes of the photoperiod, the following two experiments were performed. Experiment I: Age-matched female hamsters were exposed to either short (8L:16D) or long days (16L:8D) for 38 weeks. Initially, the short-day group showed a decline in body weight, associated with changes in gonadal function and fur color. This was not maintained by the short-day group which returned, on the most part, to long-day levels, thus becoming insensitive to this regressive lighting regimen. The time courses of these events compare well with those observed in males, which suggests a common mechanism. Experiment II: Two groups of female hamsters were exposed for 8 weeks to either long days or short days. At the end of the test period, the diurnal variations in pineal content of melatonin, serotonin, hydroxyindole acetic acid, and serum melatonin were estimated, revealing marked differences between the two groups. Not only was there a prolongation of melatonin synthesis observed in the short-day animals, but there was also a significant elevation of the melatonin levels when compared to the long-day animals. Together with recent findings in males, these findings lend support to the hypothesis that, in the Djungarian hamster, the elevation of nocturnal melatonin levels may be of additional significance, with respect to the physiological changes induced by short-day photoperiods.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionsupporting

confidence: 64%

Influence of Photoperiod on Pineal Melatonin Synthesis, Fur Color, Body Weight, and Reproductive Function in the Female Djungarian Hamster, Phodopus sungorus

Lerchl¹,

Schlatt²

1993

Neuroendocrinology

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“…A degree of bimodality in melatonin rhythm profiles has been previously demonstrated in various species, including sheep, humans, mice and hamsters under various conditions (15, 18, 31, 32). However, in all these cases, the multiple peaks were either temporally overlapping and/or asymmetric in magnitude.…”

Section: Discussionmentioning

confidence: 81%

Twice Daily Melatonin Peaks in Siberian but not Syrian Hamsters under 24 h Light:Dark:Light:Dark Cycles

Raiewski

Elliott²,

Evans

et al. 2012

Chronobiology International

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The daily pattern of blood borne melatonin varies seasonally under the control of a multi-oscillator circadian pacemaker. Here we examine patterns of melatonin secretion and locomotor activity in Siberian and Syrian hamsters entrained to bimodal LDLD8:4:8:4 and LD20:4 lighting schedules that facilitate novel temporal arrangements of component circadian oscillators. Under LDLD, both species robustly bifurcated wheel-running activity in distinct day scotophase (DS) and night scotophase (NS) bouts. Siberian hamsters displayed significant melatonin increases during each scotophase in LDLD, and in the single daily scotophase of LD20:4. The bimodal melatonin secretion pattern persisted in acutely extended 16 h scotophases. Syrian hamsters, in contrast, showed no significant increases in plasma melatonin during either scotophase of LDLD8:4:8:4 or in LD20:4. In this species, detectable levels were observed only when the day scotophase of LDLD was acutely extended to yield 16 h of darkness. Established species differences in the phase lag of nocturnal melatonin secretion relative to activity onset may underlie the above contrast: In non-bifurcated entrainment to 24 h LD cycles, Siberian hamsters show increased melatonin secretion within ~ 2 h after activity onset, whereas in Syrian hamsters, detectable melatonin secretion phase lags activity onset and the L/D transition by at least 4 h. The present results provide new evidence indicating multi-oscillator regulation of the waveform of melatonin secretion, specifically, the circadian control of the onset, offset, and duration of nocturnal secretion.

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“…Long-day breeders, such as the hamster, are reproductively active during the summer, when the nights are shorter; in these species the reproductive function decreases to a minimum in winter months, when the nights are longer (Silman, 1993). By exposing hamsters to short photoperiods, inhibition of the reproductive system is obtained until there is testicular involution in males and anoestrus in females (Hoffman, 1973;Lerchl and Nieschlag, 1992). The gonadal regression is followed by a return to normal function, suggesting the development of insensitivity of the reproductive axis to regressive photoperiods (Lerchl and Nieschlag, 1992;Lerchl and Schlatt, 1993).…”

Section: Role Of the Pineal In Reproduction The Pineal In Seasonal Anmentioning

confidence: 99%

The pineal gland and reproduction

Aleandri

Spina²,

Morini³

1996

Human Reproduction Update

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The hormonal activity of the pineal gland is influenced by both the dark-light cycle and the seasonal cycle, causing it to play an important role in the neuroendocrine control of reproductive physiology. This is especially evident in seasonally breeding animals, in which reproductive function is clearly influenced by seasonal variations in the duration of night and day. Humans are not seasonal breeders. Nevertheless, seasonal fluctuations have been described in human reproduction, and the pineal gland also appears to exert an important role in the neuroendocrine regulation of human reproductive physiology. There is evidence that the epiphysis is involved in the control of sexual maturation. In rats, the maternal pineal appears to influence the gonadal and genital development and function of offspring; this hypothesis has yet to be confirmed in humans. The pineal apparently influences human reproductive function not only at the hypothalamic-pituitary level, by inhibition of the hypothalamic pulsatile secretion of gonadotrophin-releasing hormone, but also at the gonadal level, where melatonin receptors have also been found. In addition, melatonin is reported to increase serum prolactin concentrations in both rats and humans. It has been suggested that melatonin is involved in the control of menstrual cyclicity.

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Interruption of nocturnal pineal melatonin synthesis in spontaneous recrudescent Djungarian hamsters (Phodopus sungorus)

Cited by 15 publications

References 29 publications

Influence of Photoperiod on Pineal Melatonin Synthesis, Fur Color, Body Weight, and Reproductive Function in the Female Djungarian Hamster, Phodopus sungorus

Influence of Photoperiod on Pineal Melatonin Synthesis, Fur Color, Body Weight, and Reproductive Function in the Female Djungarian Hamster, Phodopus sungorus

Twice Daily Melatonin Peaks in Siberian but not Syrian Hamsters under 24 h Light:Dark:Light:Dark Cycles

The pineal gland and reproduction

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