Photoperiod influences the central effects of ghrelin on food intake, GH and LH secretion in sheep

Joanne L. Harrison, David W. Miller, Patricia A. Findlay, Clare L. Adam

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Ghrelin is a circulating peptide, primarily secreted by the gut, that has reported actions within the hypothalamo-pituitary axis to stimulate food intake, inhibit GnRH/LH secretion and stimulate GH secretion in monogastric species. Here, we examine responses to centrally administered ghrelin in a seasonal ruminant. Estradiol-implanted castrated male sheep with indwelling intracerebroventricular (i.c.v.) cannulae were kept with unrestricted food for 16 weeks in long day photoperiod (LD, 16 h light/day) then 16 weeks in short days (SD, 8 h light/day). In week 16 of each photoperiod they were given a control (saline) i. c. v. injection on day 1 and ghrelin i. c. v. injection on day 2. Mean circulating endogenous plasma ghrelin concentrations showed no diurnal pattern and were similar between the photoperiods. Central ghrelin injection increased voluntary food intake 2-fold in the first hour after administration in LD but not in SD, decreased LH pulse frequency and amplitude in SD but not in LD, and stimulated GH release in both photoperiods, although there was a 1.5-fold larger response in LD. Therefore, central injection of ghrelin to sheep acutely stimulated food intake in LD, suppressed reproductive neuroendocrine output in SD, and stimulated GH secretion irrespective of photoperiod, although more pronounced in LD. These data indicate that photoperiod can influence hypothalamic appetite and reproductive neuroendocrine responses to ghrelin in seasonal species. Copyright (c) 2007 S. Karger AG, Basel.

Original languageEnglish
Pages (from-to)182-192
Number of pages11
JournalNeuroendocrinology
Volume87
Issue number3
Early online date10 Dec 2007
DOIs
Publication statusPublished - Apr 2008

Keywords

  • ghrelin
  • food intake
  • luteinizing hormone
  • growth hormone
  • luteinizing-hormone secretion
  • gonadotropin-releasing-hormone
  • dog nyctereutes-procyonoides
  • growth-hormone
  • intracerebroventricular leptin
  • messenger-RNA
  • body-weight
  • short-term
  • in-vivo
  • expression

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