Melatonin‐Dependent Timing of Seasonal Reproduction by the Pars Tuberalis: Pivotal Roles for Long Daylengths and Thyroid Hormones

@article{Dardente2012MelatoninDependentTO,
  title={Melatonin‐Dependent Timing of Seasonal Reproduction by the Pars Tuberalis: Pivotal Roles for Long Daylengths and Thyroid Hormones},
  author={Hugues Dardente},
  journal={Journal of Neuroendocrinology},
  year={2012},
  volume={24}
}
  • H. Dardente
  • Published 1 February 2012
  • Biology
  • Journal of Neuroendocrinology
Most mammals living at temperate latitudes exhibit marked seasonal variations in reproduction. In long‐lived species, it is assumed that timely physiological alternations between a breeding season and a period of sexual rest depend upon the ability of day length (photoperiod) to synchronise an endogenous timing mechanism called the circannual clock. The sheep has been extensively used to characterise the time‐measurement mechanisms of seasonal reproduction. Melatonin, secreted only during the… 
Neuroendocrine correlates of the critical day length response in the Soay sheep
TLDR
The transduction of progressive changes in photoperiod into transitions in endocrine output is an emergent property of a multistep signalling cascade within the mammalian neuroendocrine system.
Thyroid Hormone and Seasonal Rhythmicity
TLDR
The evidence that a circadian clock within the pars tuberalis of the adenohypophysis links photoperiod decoding to local changes of TH signaling within the medio-basal hypothalamus (MBH) through a conserved thyrotropin/deiodinase axis is reviewed.
GnRH and the photoperiodic control of seasonal reproduction: Delegating the task to kisspeptin and RFRP‐3
TLDR
Current understanding of the cellular, molecular and neuroendocrine players, which keep track of photoperiod and ultimately govern GnRH output and seasonal breeding are summarized.
The role of photoperiod and melatonin in the control of seasonal reproduction in mammals
TLDR
The collected results suggest that melatonin, kisspeptins, gonadotropin-releasing hormone (GnRH), sex hormones and thyroid hormones participate in the regulation of seasonal reproduction in mammals.
RFRP Neurons – The Doorway to Understanding Seasonal Reproduction in Mammals
TLDR
Central chronic administration of RFRP-3 in short day-adapted male Syrian hamsters fully reactivates the reproductive axis despite photoinhibitory conditions, which highlights the importance of the seasonal changes in R FRP expression for proper regulation of the reproductiveaxis.
Discontinuity in the molecular neuroendocrine response to increasing daylengths in Ile‐de‐France ewes: Is transient Dio2 induction a key feature of circannual timing?
TLDR
Molecular characterisation of the photoperiodic changes in the pituitary and hypothalamus of ovariectomised, oestradiol‐implanted Ile‐de‐France ewes shows a progressive suppression of Kiss1 in the hypothalamic arcuate nucleus and luteinising hormone/follicle‐stimulating hormone release by the pituitsary, despite apparently unchanged Dio2 expression in tanycytes.
Photoperiod is involved in the regulation of seasonal breeding in male water voles (Arvicola terrestris).
TLDR
This study characterizes neuroendocrine and anatomical markers of seasonal reproductive rhythmicity in male water voles and further suggests that these seasonal changes are chiefly driven by photoperiod.
RFRP neurons are critical gatekeepers for the photoperiodic control of reproduction
TLDR
The expression of a recently discovered neuronal population, namely RFamide-related peptide (rfrp) neurons, present in the mediobasal hypothalamus, is strongly down-regulated by melatonin in short day conditions, but not altered by circulating levels of sex steroids.
The pars tuberalis: The site of the circannual clock in mammals?
...
...

References

SHOWING 1-10 OF 243 REFERENCES
Photoperiodic synchronization of a circannual reproductive rhythm in sheep: identification of season-specific time cues.
TLDR
The results support the concept that there is a seasonal specificity with regard to the photoperiodic cues that synchronize the circannual rhythm of reproductive neuroendocrine activity in the ewe.
Hypothalamic thyroid hormones: mediators of seasonal physiology.
TLDR
This issue of Endocrinology, Barrett et al. have used small micro-implants of T3 applied locally within the hypothalamus and then exposed the hamsters to short photoperiods to understand how the seasonal melatonin signal may be interpreted by the neuroendocrine axes.
Does a Melatonin‐Dependent Circadian Oscillator in the Pars Tuberalis Drive Prolactin Seasonal Rhythmicity?
TLDR
This review summarises current knowledge of the morphological, functional and molecular aspects of the PT and considers its role in seasonal timing and the strengths and weaknesses of current hypotheses.
Circadian rhythms and photoperiodic time measurement in mammals.
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, and the extent to which the SCN and the Pineal gland may participate in the time measuring process per se remains to be determined.
Circadian rhythms and photoperiodic time measurement in mammals.
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.
Neuroendocrine mechanism of seasonal reproduction in birds and mammals.
  • T. Yoshimura
  • Biology, Environmental Science
    Animal science journal = Nihon chikusan Gakkaiho
  • 2010
TLDR
Findings suggest that although the light input pathway is different between birds and mammals (i.e. light or melatonin), the core mechanisms are conserved in these vertebrates.
Seasonality of reproduction in sheep and its control by photoperiod.
TLDR
Seasonality of the reproductive cycle in sheep is a general phenomenon for mid-latitude breeds and melatonin secretion is used by sheep for measuring daylength, however, that secretion disappears during two set points during the day, thus raising the possibility of using alternatively melatonin and light pulse for controlling the reproductive Cycle in sheep.
Importance of Photoperiodic Signal Quality to Entrainment of the Circannual Reproductive Rhythm of the Ewe1
TLDR
The inability of the winter pattern to do so indicates that the mere presence of a circadian melatonin pattern, in itself, is insufficient for entrainment of the circannual rhythm of reproductive neuroendocrine activity in the ewe.
...
...