Orexin gene expression and regulation by photoperiod in the sheep hypothalamus

Hypothalamic orexin gene expression has not been reported in the ruminant. Here, we describe the localization of preproorexin mRNA in the ovine lateral hypothalamic area (LHA) and zona incerta (ZI) using in situ hybridization. The hypothalamic localization of the orexin gene expression was similar i...

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Bibliographic Details
Published in:Regulatory peptides 2002-03, Vol.104 (1), p.41-45
Main Authors: Archer, Zoe A, Findlay, Patricia A, Rhind, Stewart M, Mercer, Julian G, Adam, Clare L
Format: Article
Language:English
Subjects:
Animals
Appetite - physiology
Carrier Proteins - biosynthesis
Carrier Proteins - genetics
Estradiol - physiology
Food intake
Gene Expression Regulation
Hypothalamus - physiology
In Situ Hybridization - methods
Intracellular Signaling Peptides and Proteins
Lateral hypothalamic area
Male
Neuropeptides - biosynthesis
Neuropeptides - genetics
Orexins
Ovine
Photoperiod
Protein Precursors - biosynthesis
Protein Precursors - genetics
Reproduction - physiology
RNA, Messenger - biosynthesis
Seasons
Sheep
Zona incerta
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Summary:Hypothalamic orexin gene expression has not been reported in the ruminant. Here, we describe the localization of preproorexin mRNA in the ovine lateral hypothalamic area (LHA) and zona incerta (ZI) using in situ hybridization. The hypothalamic localization of the orexin gene expression was similar in sheep to rodent models. Since appetite in sheep is seasonally (photoperiodically) regulated, we compared the amounts of preproorexin mRNA between long- (LD) and short-day (SD) photoperiods in both freely feeding (food intake is 20% higher in LD than SD) and food-restricted sheep (50% liveweight maintenance for 11 weeks). Gene expression was higher in SDs than in LDs but was not affected by chronic food restriction. In a second study, hypothalamic orexin gene expression in castrate sheep was not affected by a 4-day fast, irrespective of gonadal steroid (estradiol) replacement, and was not affected by the gonadal steroid per se. The results demonstrate the sensitivity of orexin gene expression to photoperiod, but up-regulation occurs in SDs when the appetite is characteristically low and no sensitivity to imposed changes in food intake. This supports the concept that orexins may not have a primary role in appetite regulation and correction of negative energy balance but since the sheep breed only in SDs, their role in seasonal reproductive activation deserves further study.
ISSN:0167-0115
1873-1686
DOI:10.1016/S0167-0115(01)00347-0