Journal of Animal Science, Vol 79, Issue 6 1573-1577, Copyright © 2001 by American Society of Animal Science

JOURNAL ARTICLE

Effect of intracerebroventricular orexin-B on food intake in sheep

J. L. Sartin, C. Dyer, R. Matteri, D. Buxton, F. Buonomo, M. Shores, J. Baker, J. A. Osborne, T. Braden and B. Steele
Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, AL 36849-5518, USA. sartijl@vetmed.auburn.edu

Orexin is a hypothalamic neuropeptide that regulates feeding behavior in rats. Orexin-B has recently been cloned in pigs and was shown to stimulate food intake after intramuscular injection. This study was designed to determine whether intracerebroventricular (ICV) and intravenous injections of orexin could regulate appetite in sheep. Suffolk wethers were moved to indoor facilities, adapted to diets for 6 wk, and trained to stand in stanchions for 3 to 6 h each day for 2 wk before indwelling ICV cannulas were installed. These sheep were provided water and they consumed feed ad libitum. On the day before an experiment, each sheep was cannulated in a jugular vein. On the day of an experiment, sheep were placed in stanchions and allowed to stand for 1 h before use. Sheep were then monitored over a 2-h control period before i.v. injection with saline or porcine orexin-B (3 micrograms/kg BW) or ICV injection with artificial cerebrospinal fluid (CSF), orexin (0.03, 0.3, or 3 micrograms/kg BW) or in a second experiment with either orexin B (0.03, 0.3, 3 micrograms/kg BW), neuropeptide-Y (NPY; 0.3 microgram/kg BW), or orexin plus NPY. Food intake was monitored for consecutive 2-h periods. The i.v. injections of orexin did not affect food intake or metabolite or hormone concentrations. In ICV sheep, orexin increased food intake at 2 (P < 0.04) and at 4 h (P < 0.02). Food intake was greatest with the 0.3 microgram/kg BW dosage of orexin (P < 0.05). In the first 2 h after injection, orexin had an effect similar to that of NPY (0.23 kg for orexin and 0.2 kg for NPY). The combination of NPY and orexin had a greater effect on food intake (to 0.34 kg) than did either orexin (P < 0.05) or NPY (P < 0.008) alone. Differences were not apparent in the subsequent 2-h interval. No differences were noted in free fatty acid, glucose, growth hormone, luteinizing hormone, or insulin concentrations following orexin injection. There was an effect of ICV orexin treatment on plasma cortisol concentrations (P < 0.002). Cortisol was increased by orexin at the 0- to 2-h (P < 0.008) and in the 2- to 4-h (P < 0.009) intervals after orexin injection. These data indicate that central administration of orexin stimulates feed intake in sheep.

This article has been cited by other articles:

				J. L. Sartin, D. L. Marks, C. D. McMahon, J. A. Daniel, P. Levasseur, C. G. Wagner, B. K. Whitlock, and B. P. Steele Central role of the melanocortin-4 receptors in appetite regulation after endotoxin J Anim Sci, October 1, 2008; 86(10): 2557 - 2567. [Abstract] [Full Text] [PDF]

				C. J. Kojima, J. A. Carroll, R. L. Matteri, K. J. Touchette, and G. L. Allee Effects of weaning and weaning weight on neuroendocrine regulators of feed intake in pigs J Anim Sci, September 1, 2007; 85(9): 2133 - 2139. [Abstract] [Full Text] [PDF]

				J. Iqbal, T. R. Manley, P. Ciofi, and I. J. Clarke Reduction in Adiposity Affects the Extent of Afferent Projections to Growth Hormone-Releasing Hormone and Somatostatin Neurons and the Degree of Colocalization of Neuropeptides in Growth Hormone-Releasing Hormone and Somatostatin Cells of the Ovine Hypothalamus Endocrinology, November 1, 2005; 146(11): 4776 - 4785. [Abstract] [Full Text] [PDF]

				I. J. Clarke, A. Rao, Y. Chilliard, C. Delavaud, and G. A. Lincoln Photoperiod effects on gene expression for hypothalamic appetite-regulating peptides and food intake in the ram Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2003; 284(1): R101 - R115. [Abstract] [Full Text] [PDF]