title: Food restriction selectively increases hypothalamic orexin-B levels in lactating rats.
abstract: Orexins are hypothalamic peptides implicated in the regulation of ingestive and other behaviours. Here we investigated prepro-orexin expression and hypothalamic orexin-A and -B levels in lactating rats, which display marked hyperphagia, with or without food restriction for 2 days or treatment with bromocriptine, which inhibits milk production and thus reduces the energy losses of lactation. Neither prepro-orexin gene expression nor hypothalamic orexin-A peptide levels were changed in any of these lactating groups compared with age-matched virgin controls. However, hypothalamic orexin-B levels were significantly higher in lactating rats that were food-restricted for 2 days (P<0.05) compared with non-lactating controls and with lactating rats that were either freely-fed or bromocriptine-treated. Thus, food restriction superimposed on lactation selectively increases hypothalamic orexin-B levels, suggesting that orexin-A and -B may be differentially released or cleared. Changes in orexin-B availability may influence physiological activities other than energy homeostasis, perhaps inducing arousal.
authors.affiliation: Diabetes and Endocrinology Research Group, Department of Medicine, Daulby Street, University of Liverpool, Liverpool L69 3GA, UK. xjcai@liv.ac.uk
authors.forename: X J
authors.initials: XJ
authors.lastname: Cai
authors.forename: R
authors.initials: R
authors.lastname: Denis
authors.forename: R G
authors.initials: RG
authors.lastname: Vernon
authors.forename: J C
authors.initials: JC
authors.lastname: Clapham
authors.forename: S
authors.initials: S
authors.lastname: Wilson
authors.forename: J R
authors.initials: JR
authors.lastname: Arch
authors.forename: G
authors.initials: G
authors.lastname: Williams
mesh_terms: D000818:Animals; D002149:Energy Intake; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D007774:Lactation; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D000068797:Orexins; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D012333:RNA, Messenger