Melatonin-independent Photoperiodic Entrainment of the Circannual TSH Rhythm in the Pars Tuberalis of the European Hamster
| Autor: | Valérie Simonneaux, Stefanie Monecke, Cristina Sáenz de Miera, Dominique Sage-Ciocca, Paul Pévet |
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| Rok vydání: | 2018 |
| Předmět: |
Male
0301 basic medicine endocrine system medicine.medical_specialty Physiology Photoperiod DIO2 Thyrotropin beta Subunit Biology Pineal Gland Melatonin 03 medical and health sciences Pineal gland 0302 clinical medicine Kisspeptin Cricetinae Physiology (medical) Internal medicine medicine Animals Circadian rhythm photoperiodism Chronobiology Circadian Rhythm 030104 developmental biology Endocrinology medicine.anatomical_structure Seasons Pars tuberalis hormones hormone substitutes and hormone antagonists 030217 neurology & neurosurgery medicine.drug |
| Zdroj: | Journal of Biological Rhythms. 33:302-317 |
| ISSN: | 1552-4531 0748-7304 |
| DOI: | 10.1177/0748730418766601 |
| Popis: | Adaptation of biological rhythms to a seasonal environment in circannual mammals is achieved via the synchronization of intrinsic circannual rhythms to the external year by photoperiod. In mammals, the photoperiodic information is integrated to seasonal physiology via the pineal hormone melatonin regulation of pars tuberalis (PT) TSHβ expression and its downstream control of hypothalamic dio2 gene expression. In the circannual European hamster, however, photoperiodic entrainment of the circannual clock is possible in pinealectomized animals. The present study explores whether the TSHβ expression in the PT and the downstream hypothalamic pathways are regulated by photoperiod in European hamsters in the absence of melatonin. All animals were kept on an accelerated photoperiodic regime, which compressed the natural year to a 6-month cycle. Sham-operated European hamsters and half of the pinealectomized European hamsters entrained their annual cycle in reproduction, body weight, and activity pattern to this cycle, whereas the other half of the pinealectomized animals followed only each second cycle. In all animals, PT TSHβ and hypothalamic dio2 expressions were higher in hamsters displaying a summer physiological state than in those in winter state. Moreover, in agreement with their seasonal state, reproductive animals (summer state) showed higher expression of rfrp and lower expression of kiss1-genes encoding central regulators of the reproductive axis-than those animals in reproductive quiescence (winter state), indicating the hypothalamic integration of the photoperiodic signal even in pinealectomized animals. The appropriate occurrence of a well-characterized activity pattern indicative of a so-called sensitive phase to short photoperiod suggested that the SCN constructs the melatonin-independent photoperiodic message. This message is sufficient to entrain the circannual rhythm in TSHβ expression in the PT and the downstream hypothalamic neuroendocrine pathway through a yet unknown pathway. These results reinforce the hypothesis that the PT is the site for the integration of circannual and photoperiodic information. |
| Databáze: | OpenAIRE |
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