Localization of the thyrotropin releasing hormone (TRH) secretory system in the Siberian hamster

Francis J. P. Ebling, Dana Lorraine Wilson, Joanne Wood, Debbie Hughes, Julian Mercer, Perry Barrett

Research output: Contribution to journalArticle

Abstract

Thyrotropin releasing hormone (TRH) not only plays an essential role in the regulation of the pituitary–thyroid axis, but may also exert complementary effects on energy metabolism within the central nervous system. It has been hypothesised that in seasonal mammals such as the Siberian hamster, increased activity of the TRH secretory system contributes to winter adaptations whereby food intake is decreased, and catabolism of fat stores increases to support thermogenesis. The aim of this study was therefore to determine the anatomical distribution of TRH producing neurons and TRH-R1 receptor distribution in the hypothalamus of the Siberian hamster. A partial sequence encoding TRH-R1 was cloned from hamster hypothalamic cDNA and used to generate a riboprobe for in situ hybridization studies. This was complemented by immunocytochemical mapping of TRH-immunoreactive cell soma and processes and in situ hybridization analysis of the localization of a rat preproTRH riboprobe. TRH-ir cell soma and mRNA expression were found to be widely distributed throughout the hypothalamus, with particular aggregations in the paraventricular nucleus, the medial preoptic area and periventricular nucleus, and in the dorsomedial hypothalamus extending into the lateral hypothalamic area. There was dense innervation of TRH projections at the median eminence, consistent with the role of TRH as a hypothalamic-releasing hormone, but there was also widespread innervation of many other areas in particular the preoptic area, anterior hypothalamic area and dorsomedial hypothalamus. Likewise, TRH-R1 mRNA expressing cells were abundant throughout the hypothalamus, both in the regions highly innervated by TRH-ir fibers and throughout the arcuate nucleus. This wide distribution of TRH-producing and receptive cells in the hypothalamus is consistent with its hypothesised neuromodulatory roles in the control of appetite, thermoregulation, energy expenditure, and thus ultimately body weight. (Supported by BBSRC/SEERAD project Grants 42/S17106 and BBS/B/10765.)

Original languageEnglish
Pages (from-to)9-10
Number of pages2
JournalFrontiers in Neuroendocrinology
Volume27
Issue number1
DOIs
Publication statusPublished - May 2006

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