The thyrotropin-releasing hormone secretory system in the hypothalamus of the Siberian hamster in long and short photoperiods

F. J. P. Ebling, D. Wilson, J. Wood, D. Hughes, Julian Mercer, Peter John Morgan, Perry Barrett

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Thyrotropin-releasing hormone (TRH) is not only essential for the regulation of the pituitary-thyroid axis, but also exerts complementary effects on energy metabolism within the brain. We hypothesised that increased activity of the TRH secretory system may contribute to seasonal adaptations in the Siberian hamster whereby food intake is decreased in winter, and catabolism of fat stores is increased to support thermogenesis. We determined the distribution of TRH producing neurones and TRH-R1 receptor expressing cells in the hypothalamus, and investigated whether photoperiod regulated this system. TRH-immunoreactive (ir) cell somata and preproTRH mRNA expression were found to be widely distributed throughout the medial hypothalamus, with particular clusters in the paraventricular nucleus, the medial preoptic area and periventricular nucleus, and in the dorsomedial hypothalamus extending into the lateral hypothalamic area. A partial sequence encoding TRH-R1 was cloned from hamster hypothalamic cDNA and used to generate a riboprobe for in situ hybridisation studies. TRH-R1 mRNA expressing cells were abundant throughout the hypothalamus, corresponding to the widespread presence of TRH-ir fibres. Photoperiod did not affect the expression of preproTRH mRNA in any region, and the only significant change in TRH-R1 expression was in the dorsomedial posterior arcuate region. This wide distribution of TRH-producing and receptive cells in the hypothalamus is consistent with its hypothesised neuromodulatory roles in the short-term homeostatic control of appetite, thermoregulation and energy expenditure, but the lack of photoperiodic change in TRH mRNA expression does not support the hypothesis that changes in this system underlie long-term seasonal changes in body weight.

Original languageEnglish
Pages (from-to)576-586
Number of pages11
JournalJournal of Neuroendocrinology
Volume20
Issue number5
Early online date17 Mar 2008
DOIs
Publication statusPublished - May 2008

Keywords

  • hypothalamus
  • immunohistochemistry
  • in situ hybridisation
  • thyroid
  • messenger-ribonucleic-acid
  • central-nervous-system
  • body-weight
  • rat-brain
  • paraventricular nucleus
  • arcuate nucleus
  • gene-expression
  • energy-balance
  • food-intake
  • (TRH)-immunoreactive structures

Cite this

The thyrotropin-releasing hormone secretory system in the hypothalamus of the Siberian hamster in long and short photoperiods. / Ebling, F. J. P.; Wilson, D.; Wood, J.; Hughes, D.; Mercer, Julian; Morgan, Peter John; Barrett, Perry.

In: Journal of Neuroendocrinology, Vol. 20, No. 5, 05.2008, p. 576-586.

Research output: Contribution to journalArticle

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T1 - The thyrotropin-releasing hormone secretory system in the hypothalamus of the Siberian hamster in long and short photoperiods

AU - Ebling, F. J. P.

AU - Wilson, D.

AU - Wood, J.

AU - Hughes, D.

AU - Mercer, Julian

AU - Morgan, Peter John

AU - Barrett, Perry

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N2 - Thyrotropin-releasing hormone (TRH) is not only essential for the regulation of the pituitary-thyroid axis, but also exerts complementary effects on energy metabolism within the brain. We hypothesised that increased activity of the TRH secretory system may contribute to seasonal adaptations in the Siberian hamster whereby food intake is decreased in winter, and catabolism of fat stores is increased to support thermogenesis. We determined the distribution of TRH producing neurones and TRH-R1 receptor expressing cells in the hypothalamus, and investigated whether photoperiod regulated this system. TRH-immunoreactive (ir) cell somata and preproTRH mRNA expression were found to be widely distributed throughout the medial hypothalamus, with particular clusters in the paraventricular nucleus, the medial preoptic area and periventricular nucleus, and in the dorsomedial hypothalamus extending into the lateral hypothalamic area. A partial sequence encoding TRH-R1 was cloned from hamster hypothalamic cDNA and used to generate a riboprobe for in situ hybridisation studies. TRH-R1 mRNA expressing cells were abundant throughout the hypothalamus, corresponding to the widespread presence of TRH-ir fibres. Photoperiod did not affect the expression of preproTRH mRNA in any region, and the only significant change in TRH-R1 expression was in the dorsomedial posterior arcuate region. This wide distribution of TRH-producing and receptive cells in the hypothalamus is consistent with its hypothesised neuromodulatory roles in the short-term homeostatic control of appetite, thermoregulation and energy expenditure, but the lack of photoperiodic change in TRH mRNA expression does not support the hypothesis that changes in this system underlie long-term seasonal changes in body weight.

AB - Thyrotropin-releasing hormone (TRH) is not only essential for the regulation of the pituitary-thyroid axis, but also exerts complementary effects on energy metabolism within the brain. We hypothesised that increased activity of the TRH secretory system may contribute to seasonal adaptations in the Siberian hamster whereby food intake is decreased in winter, and catabolism of fat stores is increased to support thermogenesis. We determined the distribution of TRH producing neurones and TRH-R1 receptor expressing cells in the hypothalamus, and investigated whether photoperiod regulated this system. TRH-immunoreactive (ir) cell somata and preproTRH mRNA expression were found to be widely distributed throughout the medial hypothalamus, with particular clusters in the paraventricular nucleus, the medial preoptic area and periventricular nucleus, and in the dorsomedial hypothalamus extending into the lateral hypothalamic area. A partial sequence encoding TRH-R1 was cloned from hamster hypothalamic cDNA and used to generate a riboprobe for in situ hybridisation studies. TRH-R1 mRNA expressing cells were abundant throughout the hypothalamus, corresponding to the widespread presence of TRH-ir fibres. Photoperiod did not affect the expression of preproTRH mRNA in any region, and the only significant change in TRH-R1 expression was in the dorsomedial posterior arcuate region. This wide distribution of TRH-producing and receptive cells in the hypothalamus is consistent with its hypothesised neuromodulatory roles in the short-term homeostatic control of appetite, thermoregulation and energy expenditure, but the lack of photoperiodic change in TRH mRNA expression does not support the hypothesis that changes in this system underlie long-term seasonal changes in body weight.

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KW - immunohistochemistry

KW - in situ hybridisation

KW - thyroid

KW - messenger-ribonucleic-acid

KW - central-nervous-system

KW - body-weight

KW - rat-brain

KW - paraventricular nucleus

KW - arcuate nucleus

KW - gene-expression

KW - energy-balance

KW - food-intake

KW - (TRH)-immunoreactive structures

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DO - 10.1111/j.1365-2826.2008.01702.x

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VL - 20

SP - 576

EP - 586

JO - Journal of Neuroendocrinology

JF - Journal of Neuroendocrinology

SN - 0953-8194

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