ORIGINAL ARTICLE Oxyntomodulin reduces expression of glucagon-like peptide 1 receptor in the brainstem of chickens A. G. Moghaddam 1,2,3 , M. M. Yaghoobi 3 , H. Jonaidi 4 , M. T. Z. Mahani 3 and H. Sepehri 1 1 School of Biology, University College of Sciences, University of Tehran, Tehran Iran, 2 School of Sciences, Department of biology, Shahid Bahonar University of Kerman, Kerman, Iran, 3 Department of Biotechnology, Research Institute of Environmental Sciences, International Centre for Science, High Technology and Environmental Sciences, Kerman, Iran, and 4 Group of Basic Sciences, Faculty of Veterinary Medicine, Shahid Bahonar University of Kerman (SBUK), Kerman, Iran Introduction Food intake is controlled by different long-term and short-term regulatory mechanisms. Several gut hor- mones including ghrelin, cholecystokinin (CCK), peptide YY (PYY), glucagon-like peptide-1 (GLP-1) and oxyntomodulin (OXM) act as neurotransmitters and regulate short-term food intake(Na ¨ slund and Hellstro ¨ m, 2007). GLP-1 and OXM are produced by pre-proglucagon cleavage. These hormones are released from the endocrine intestinal cells after ingestion and act through G-protein coupled recep- tors on afferent nerves on hypothalamic arcuate nucleus (ARC) (Chaudhri et al., 2006; Na ¨slund and Hellstro ¨ m, 2007). Ghrelin potentially promotes food intake by stimulating neuropeptide Y (NPY) and agouti related protein (AgRP) in the ARC. The final effects of OXM and GLP-1 are reduction in food intake and sensation of satiety possibly by reducing signalling in the NPY and AgRP pathway (Murphy and Bloom, 2004; Stanley et al., 2005; Wynne and bloom, 2006). Glucagon-like peptide-1 binds to the GLP-1 recep- tor (GLP-1R) and raises the intracellular cyclic AMP (Gallwitz et al., 1993). OXM has no recognized exclusive receptor and binds to the GLP-1R with les- ser affinity than GLP-1. There are some evidences, which show that the effects of OXM are mediated via the GLP-1 receptor. For example, the anorectic effects of OXM are lost in GLP-1 receptor null mice and are also inhibited by co-administration of the GLP-1 receptor antagonist exendin (Meeran, 1999; Baggio et al., 2004). GLP-1 receptor transcripts are present in the cerebral cortex, caudal hippocampus, hypothalamus and many other regions of the rat central nervous system (CNS). GLP-1R mRNA is Keywords oxyntomodulin, food intake, glucagon-like peptide 1 receptor expression, brainstem, chicken Correspondence Mohammad Mahdi Yaghoobi, Department of Biotechnology, Research Institute of Environmental Sciences, International Centre for Science, High Technology and Environmental Sciences, PO Box 76315-117, Kerman, Iran. Tel: +983426226611; Fax: +983426226617; E-mail: yaghoobim@icst.ac.ir Received: 27 October 2008; accepted: 22 December 2008 Summary Oxyntomodulin (OXM) is a peptide released from the gut and attenu- ates food intake by acting on hypothalamus. However, its role at the molecular level is not well studied. In the first section of this study, we analysed the effect of OXM on food intake behaviour after injecting into the lateral ventricle of chickens. The outcome showed that food intake decreased significantly after administering 4 nmol of OXM. In the sec- ond part, the expression of glucagon-like peptide 1 receptor (GLP-1R) in the brainstem was analysed by real-time RT-PCR. The results showed that expression of GLP-1R was reduced to 27% and 16% at 30 and 90 mins after injection of OXM respectively. In saline-injected chickens, no reduction in GLP-1R was seen. It can be concluded that OXM has a down regulatory effect on the responding receptor, GLP-1R and OXM in chicks has the same reductive effect on food intake as in the mammals. DOI: 10.1111/j.1439-0396.2009.00925.x 422 Journal of Animal Physiology and Animal Nutrition 94 (2010) 422–428 ª 2009 Blackwell Verlag GmbH