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Circadian rhythms and photoperiodic time measurement in mammals.
Elliott Ja
- Vol. 35, Iss: 12, pp 2339-2346
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TLDR
The available evidence strongly suggests the participation of the pineal gland and the suprachiasmatic nucleus (SCN) in the photoperiodic regulation of mammalian reproductive cycles, however, little is known regarding concrete physiological mechanisms.Abstract:
Many mammalian species display seasonal breeding patterns correlated with annual cycles of change in the physiology and morphology of the reproductive system. Such annual reproductive cycles are often photoperiodically controlled (i.e, the annual change in day length determines when reproductive activity begins and when it ends within the annual cycle). Photoperiodic control of seasonally appropriate changes in reproductive activity is dependent on an endogenous time measuring process. Among mammals the physiological basis of photoperiodic time measurement has been studied most extensively in the golden hamster. Studies with this species indicate that photoperiodic time measurement is executed by the circadian system. The time measuring process depends on a circadian oscillation of responsiveness to light with properties similar to those of the hypothetical rhythm originally proposed by Bunning to explain photoperiodic phenomena in plants. The available evidence strongly suggests the participation of the pineal gland and the suprachiasmatic nucleus (SCN) in the photoperiodic regulation of mammalian reproductive cycles. However, little is known regarding concrete physiological mechanisms, and the extent to which the SCN and the pineal gland may participate in the time measuring process per se remains to be determined.read more
Citations
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Light Suppresses Melatonin Secretion in Humans
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Mammalian Photoperiodic System: Formal Properties and Neuroendocrine Mechanisms of Photoperiodic Time Measurement
TL;DR: Variations in photoperiodic response are seen not only between species but also between breeding populations within a species and between individuals within single breeding populations, and among species differences with respect to the importance and specific functions of various melatonin target sites.
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Antidepressant and circadian phase-shifting effects of light
TL;DR: The antidepressant response to morning light was accompanied by an advance in the onset of nighttime melatonin production, suggesting that timing may be critical for the antidepressant effects of bright light.
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The Reproductive Ecology of the House Mouse
TL;DR: The reproductive biology of the house mouse seems uniquely suited to support ecological opportunism, and the relatively few environmental inhibitors of reproduction in this species should enhance the ability of dispersing young to colonize an exceptionally wide variety of habitats and climates.
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Circadian rhythmicity restored by neural transplant. Immunocytochemical characterization of the graft and its integration with the host brain
TL;DR: It is shown that implantations of brain grafts containing the fetal SCN reestablish circadian rhythms of locomotor activity in adult hamsters previously made arrhythmic by SCN lesions.
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