Journal
GENERAL AND COMPARATIVE ENDOCRINOLOGY
Volume 166, Issue 1, Pages 39-46Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ygcen.2009.11.001
Keywords
Ghrelin; Teleosts; Salmonids; Appetite; Anorexia; Endocrine regulation; Body fat; CRF; CNS; Ghrelin receptor; GHS-R
Categories
Funding
- Commission of the European Communities [FOOD-CT-2004-506359]
- Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS)
- Goteborg University Research Platform on Integrative Physiology
- Helge Ax:son Johnson Foundation
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Ghrelin stimulates pituitary growth hormone (GH) release, and has a key role in the regulation of food intake and adiposity in vertebrates. To investigate the central effect of native rainbow trout ghrelin (rtghrelin) on food intake in rainbow trout, as well as its possible mode of action, four groups of fish received a single injection into the third brain ventricle (i.c.v. injection): (I) control group (physiological saline) (2) ghrelin-treated group (2.0 ng rtghrelin g bwt(-1)), (3) group given the corticotropin-releasing hormone receptor antagonist a-helical CRF 9-41 (ahCRF) (4.0 ng g bwt(-1)) and (4) group receiving the same dose of both ghrelin and ahCRF. Food intake was assessed 1 h after treatment. In addition, the presence of the GHS-R (the ghrelin receptor) in the rainbow trout CNS was examined with Western blot. To investigate peripheral effects of ghrelin, rainbow trout received an intraperitoneal cholesterol-based implant with or without rtghrelin, and daily food intake was measured during 14 days. Weight and length were measured at the start and termination of the experiment and specific growth rates were calculated. Mesenteric fat stores, muscle and liver lipid content were analysed after the treatment period. Central ghrelin injections decreased food intake compared with controls, and treatment with ahCRF abolished the ghrelin-effect. Western blot analysis of the GHS-R revealed a single band at around 60 kDa in pituitary, hypothalamus, brain and stomach. Long-term peripheral ghrelin treatment decreased daily food intake compared with controls. This was reflected in a ghrelin-induced decrease in weight growth rate (p < 0.06). There was no effect of ghrelin on plasma CH levels or tissue fat stores. The conclusion from this study is that the GHS-R is indicated in the CNS in rainbow trout and that ghrelin may act there as an anorexigenic hormone, through a CRF-mediated pathway. Elevated peripheral ghrelin levels also seem to lead to decreased feed intake in the longer term. (C) 2009 Elsevier Inc. All rights reserved.
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