Melatonin: a coordinating signal for mammalian reproduction?

@article{Tamarkin1985MelatoninAC,
  title={Melatonin: a coordinating signal for mammalian reproduction?},
  author={Lawrence Tamarkin and C J Baird and Osborne F. X. Almeida},
  journal={Science},
  year={1985},
  volume={227 4688},
  pages={
          714-20
        }
}
There is a daily rhythm in the production of the pineal hormone melatonin in all mammalian species. Production is stimulated by darkness and inhibited by light. This provides a signal reflecting the changing environmental lighting cycle. In seasonally breeding mammals that use changes in the photoperiod to time their reproductive cycles, temporal signals to the reproductive system are controlled by the daily rhythm in melatonin production. 

Effect of photoperiodism on fertility in domestic animals

TLDR
There is a daily rhythm in the production of the pineal hormone melatonin in all mammalian species, which provides a signal reflecting the changing environmental lighting cycle.

The Pineal Gland, Circadian Rhythms and Photoperiodism

TLDR
The pineal gland serves the same function in all species studied to date and conveys information concerning light-dark cycles to body physiology for the organisation of seasonal and circadian rhythms, but how the message is read at a cellular and molecular level remains largely unclear.

Generation of melatonin rhythms.

TLDR
The results confirm that the melatonin rhythm is generated endogenously and will free-run under constant darkness with a period close to 24 h for at least 10 days, and that the rhythm can be entrained by exposure to IL:23D with the end of the light period acting as the 'melatonin-on' signal, and phase-shifts in themelatonin Rhythm can be induced by phase- Shifting in the light-dark cycle.

How does melatonin control seasonal reproductive cycles 7

TLDR
Most experimental work suggests that it is the duration of high night time melatonin secretion (positively correlated with the length of the natural or artificial dark phase) which conveys the photoperiodic signal, but there appears to be a seasonal variation in sensitivity to short day melatonin effects.

Melatonin and circadian control in mammals

TLDR
Results suggest that melatonin is a potent synchronizer of rat circadian rhythms and has a direct action on the circadian pacemaker, possibly acting as an internal zeitgeber for the total circadian structure of mammals.

The melatonin rhythm: both a clock and a calendar

TLDR
The paper summarizes the 3 patterns of nocturnal melatonin production that have been described and shows that the circadian production and secretion of melatonin by the pineal gland can impart both daily and seasonal, i.e., calendar, information to the organism.

Melatonin Receptor Signaling: Finding the Path Through the Dark

TLDR
How the level of receptor expression may alter their efficacy is discussed, so that caution is necessary when extrapolating the pharmacological properties of ligands defined on recombinant systems to the receptors in the organism.

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

TLDR
The aim of this review is to gather together early and recent data on the effects of the nonadrenergic transmitters on modulation of melatonin synthesis, which reveals the variety of inputs that can be integrated by the pineal gland; what elements are crucial to deliver the very precise timing information to the organism.

Neuroendocrine Photoperiodic Processes

TLDR
Results show that during daily variations, mt1 melatonin receptor mRNA and protein are differentially regulated, while at the photoperiodic level, the mt1 protein status depends on mRNA transcription.
...

References

SHOWING 1-10 OF 114 REFERENCES

Pineal Melatonin Content throughout the Hamster Estrous Cycle 1

TLDR
A circadian rhythm in pineal melatonin content persisted throughout the estrous cycle of female hamsters maintained in a 14-hr:10-hr-dark photoperiod, and the hypothesis that pinealmelatonin production in hamsters is inhibited by estrogen feedback is not supported.

Regulation of pineal melatonin in the Syrian hamster.

TLDR
Pineal melatonin in reproductively competent males was found to exhibit a daily rhythm; night values were 10-fold higher than day values; and a difference in the phasing of the pinealmelatonin rhythm relative to the time of day was seen.

Studies on the daily pattern of pineal melatonin in the Syrian hamster.

TLDR
The rhythm in pineal melatonin appears to be truly circadian and is tightly coupled to the circadian rhythm in running activity.

Pineal melatonin secretion drives the reproductive response to daylength in the ewe.

TLDR
It is concluded that the pineal mediates the reproductive response of the ewe to inductive photoperiods through its daily rhythm of melatonin secretion.

Diurnal changes in pineal melatonin content in four rodent species: relationship to photoperiodism.

TLDR
Daily changes in pineal melatonin content were examined in four rodent species and treatment of pinealectomized Syrian hamsters with melatonin during the time of the night when pinealmelatonin content would be elevated induced gonadal regression failed to respond to exogenous melatonin.

A melatonin rhythm persists in rat pineals in darkness.

TLDR
A rhythm of pineal melatonin content persists and is phase-locked with the free-running, circadian rhythm of locomotor activity, however, the melatonin cycle was suppressed in intact rats that were maintained in continuous light.

Variation in Pineal Melatonin Content during the Estrous Cycle of the Rat

TLDR
The data indicate that the circadian pineal melatonin rhythm is a function of estrous cycle stage in the rat, and, thus, important differences exist in the pineal biosynthetic dynamics of this species relative to those of seasonal breeders such as the hamster and sheep.

Melatonin: Its Inhibition of Pineal Antigonadotrophic Activity in Male Hamsters

TLDR
The results suggest that melatonin is not the pineal antigonadotrophic factor in the male golden hamster and that pituitary levels of prolactin return to normal after pinealectomy and melatonin treatment.
...