Effect of Photoperiod on the Thyroid-Stimulating Hormone Neuroendocrine System in the European Hamster (Cricetus cricetus)

E. A. Hanon, Kevin William Routledge, Hugues Dardente, M. Masson-Pevet, Peter John Morgan, David Grey Hazlerigg

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

Recent studies have characterised a retrograde mechanism whereby the pineal hormone melatonin acts in the pars tuberalis (PT) of the pituitary gland to control thyroid hormone action in the hypothalamus, leading to changes in seasonal reproductive function. This involves the release of thyroid-stimulating hormone (TSH) from PT that activates type II deiodinase (DIO2) gene expression in hypothalamic ependymal cells, locally generating biologically active T3, and thus triggering a neuroendocrine cascade. In the present study, we investigated whether a similar regulatory mechanism operates in the European hamster. This species utilises both melatonin signalling and a circannual timer to time the seasonal reproductive cycle. We found that expression of beta TSH RNA in the PT was markedly increased under long compared to short photoperiod, whereas TSH receptor expression was localised in the ependymal cells lining the third ventricle, and in the PT, where its expression varied with time and photoperiod. In the ependymal cells at the base of the third ventricle, DIO2 and type III deiodinase (DIO3) expression was reciprocally regulated, with DIO2 activated under long and repressed under short photoperiod, and the reverse case for DIO3. These data are consistent with recent observations in sheep, and suggest that the PT TSH third ventricle-ependymal cell relay plays a conserved role in initiating the photoperiodic response in both long- and short-day breeding mammals.

Original languageEnglish
Pages (from-to)51-55
Number of pages5
JournalJournal of Neuroendocrinology
Volume22
Issue number1
Early online date14 Nov 2009
DOIs
Publication statusPublished - Jan 2010

Keywords

  • deiodinase
  • melatonin
  • pars tuberalis
  • TSH
  • seasonal reproduction
  • clock gene-expression
  • body-weight
  • day response
  • thyrotropin
  • receptor
  • rhythms
  • cells
  • rat

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