Seasonality and Melatonin Receptors in the Pars tuberalis in Some Long Day Breeders

Masson‐Pévet, Mireille; Guilhot, François

doi:10.1159/000109527

Cited by 37 publications

(26 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Annual variation in melatonin signal duration has been shown to be a critical input signal for the annual timing mechanism [81,82] that involves the pituitary and its pars tuburalis (PT), which is densely packed with melatonin receptors [83][84][85][86][87][88][89]. Pineal melatonin release is driven by the SCN via the paraventricular nucleus (PVN), superior cervical ganglion (SCG) and intermediolateral column of the spinal cord (IML) pathway [58,69].…”

Section: Adjustment To Changing Day Length As a Selection Force For Tmentioning

confidence: 99%

Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod

Hut

Beersma

2011

Phil. Trans. R. Soc. B

183

193

View full text Add to dashboard Cite

Virtually all species have developed cellular oscillations and mechanisms that synchronize these cellular oscillations to environmental cycles. Such environmental cycles in biotic (e.g. food availability and predation risk) or abiotic (e.g. temperature and light) factors may occur on a daily, annual or tidal time scale. Internal timing mechanisms may facilitate behavioural or physiological adaptation to such changes in environmental conditions. These timing mechanisms commonly involve an internal molecular oscillator (a 'clock') that is synchronized ('entrained') to the environmental cycle by receptor mechanisms responding to relevant environmental signals ('Zeitgeber', i.e. German for time-giver). To understand the evolution of such timing mechanisms, we have to understand the mechanisms leading to selective advantage. Although major advances have been made in our understanding of the physiological and molecular mechanisms driving internal cycles (proximate questions), studies identifying mechanisms of natural selection on clock systems (ultimate questions) are rather limited. Here, we discuss the selective advantage of a circadian system and how its adaptation to day length variation may have a functional role in optimizing seasonal timing. We discuss various cases where selective advantages of circadian timing mechanisms have been shown and cases where temporarily loss of circadian timing may cause selective advantage. We suggest an explanation for why a circadian timing system has emerged in primitive life forms like cyanobacteria and we evaluate a possible molecular mechanism that enabled these bacteria to adapt to seasonal variation in day length. We further discuss how the role of the circadian system in photoperiodic time measurement may explain differential selection pressures on circadian period when species are exposed to changing climatic conditions (e.g. global warming) or when they expand their geographical range to different latitudes or altitudes.

show abstract

Section: Adjustment To Changing Day Length As a Selection Force For Tmentioning

confidence: 99%

Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod

Hut

Beersma

2011

Phil. Trans. R. Soc. B

183

193

View full text Add to dashboard Cite

show abstract

“…Binding sites have been identified using 125 I-melatonin as a radioligand for autoradiographic experiments. A broad range of mammalian species has been investigated, and the total number of labelled structures is remarkably high: over 100 neural and 30 ‘peripheral’ structures bind 125 I-melatonin specifically [25,26,27,28]. Yet, considerable species differences exist, and only 2 structures are consistently labelled: the SCN and the pars tuberalis (PT) of the adenohypophysis [25,26,27,28].…”

Section: Seasonal Control Of Reproduction: From Photonic Energy To Spmentioning

confidence: 99%

“…A broad range of mammalian species has been investigated, and the total number of labelled structures is remarkably high: over 100 neural and 30 ‘peripheral’ structures bind 125 I-melatonin specifically [25,26,27,28]. Yet, considerable species differences exist, and only 2 structures are consistently labelled: the SCN and the pars tuberalis (PT) of the adenohypophysis [25,26,27,28]. In mammals, 2 high-affinity G-protein-coupled membrane melatonin receptors, MT1 and MT2, have been described so far [25,26,27,29,30,31,32].…”

Section: Seasonal Control Of Reproduction: From Photonic Energy To Spmentioning

confidence: 99%

“…Yet, considerable species differences exist, and only 2 structures are consistently labelled: the SCN and the pars tuberalis (PT) of the adenohypophysis [25,26,27,28]. In mammals, 2 high-affinity G-protein-coupled membrane melatonin receptors, MT1 and MT2, have been described so far [25,26,27,29,30,31,32]. More recently, another binding site of lower affinity, MT3, has also been purified which corresponds to the quinone reductase 2 [33, 34].…”

Section: Seasonal Control Of Reproduction: From Photonic Energy To Spmentioning

confidence: 99%

“…Up to now, no brain locus dedicated to the control of photoperiodic functions has been identified.Lesion studies have shown that seasonal timing is probably scattered in several locations and, because melatonin is an absolute requirement for seasonal timing, it is reasonable to assume that at least some of these areas should display melatonin binding sites. But apart from the PT and the SCN, binding sites differ greatly from one species to another [25,26,27,28]. Researchers have lacked an important investigation tool, since the development of specific antibodies for melatonin receptors has never been entirely successful in seasonal models, such as hamsters or sheep.…”

Section: Seasonal Control Of Reproduction: From Photonic Energy To Spmentioning

confidence: 99%

See 2 more Smart Citations

Melatonin Controls Seasonal Breeding by a Network of Hypothalamic Targets

et al. 2009

Self Cite

View full text Add to dashboard Cite

In seasonal species, the photoperiod (i.e. day length) tightly regulates reproduction to ensure that birth occurs at the most favourable time of year. In mammals, a distinct photoneuroendocrine circuit controls this process via the pineal hormone melatonin. This hormone is responsible for the seasonal timing of reproduction, but the anatomical substrates and the cellular mechanisms through which melatonin modulates seasonal functions remain imprecise. Recently, several genes have been identified as being regulated by the photoperiod in the brain of seasonal mammals. These genes are thought to play active roles in the regulation of seasonal biology, notably for the adjustment of reproduction and body weight. Here, we briefly review findings associated with the control of seasonal breeding and describe recent data ascribing photoperiodic roles to type 2 and type 3 deiodinases, to the Kiss1/GPR54 system and to the RFamide-related peptides.Interestingly, these systems involve different hypothalamic nuclei, suggesting that several brain loci may be crucial for melatonin to regulate reproduction, and thus represent key starting points to identify the long-sought-after mode and site(s) of action of melatonin. Such findings raise great hopes for the future and could herald a new era of research in the field of seasonal biology.

show abstract

Hypophysial angiogenesis decodes annual time and underlies physiological adaptation to seasonal changes in the environment

Tortonese

2022

J Exp Zool Pt A

View full text Add to dashboard Cite

Adaptation to annual changes in the environment is controlled by hypophysial hormones. In temperate zones, photoperiod is the primary external cue that regulates annual biological cycles and is translated by the pattern of melatonin secretion acting primarily in the hypophysial pars tuberalis. Angiogenic mechanisms within this tissue contribute to decode the melatonin signal through alternative splicing of the vascular endothelial growth factor A (VEGF-A) gene in both the pars tuberalis and the capillary loops of the infundibulum. The resulting melatonin-evoked differential productions of VEGF-A isoforms will induce seasonal remodeling of the vascular connection between the hypothalamus and hypophysis, and act as paracrine messengers in the pars distalis to generate the required seasonal endocrine response. Specifically, the long melatonin signal in winter upregulates antiangiogenic VEGF-A isoforms, which will reduce the number of vascular loops and the density of VEGF receptors in endocrine and folliculo-stellate (FS) cells, inhibit prolactin secretion, and stimulate FSH. In contrast, the short melatonin signal in summer upregulates proangiogenic VEGF-A isoforms that will increase the number of vascular loops and the density of VEGF receptors in endocrine and FS cells, stimulate prolactin secretion, and suppress FSH. A similar system has been identified in long day seasonal breeders, revealing that this is a conserved mechanism of adaptation across species. Thus, an angiogenesis-based, intrahypophysial system for annual time measurement controls local microvascular plasticity and conveys the photoperiodic signal readout from the melatonin sensitive pars tuberalis to the endocrine cells of the pars distalis to regulate seasonal adaptation to the environment.

show abstract

Seasonality and Melatonin Receptors in the Pars tuberalis in Some Long Day Breeders

Cited by 37 publications

References 45 publications

Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod

Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod

Melatonin Controls Seasonal Breeding by a Network of Hypothalamic Targets

Hypophysial angiogenesis decodes annual time and underlies physiological adaptation to seasonal changes in the environment

Contact Info

Product

Resources

About