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Selected hormonal and neurotransmitter mechanisms regulating feed intake in sheep

Published online by Cambridge University Press:  22 July 2010

J. L. Sartin ,
J. A. Daniel ,
B. K. Whitlock  and
R. R. Wilborn
J. L. Sartin*
Affiliation:
Department of Anatomy, Physiology & Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
J. A. Daniel
Affiliation:
Department of Animal Science, Berry College, Mt. Berry, GA 30149, USA
B. K. Whitlock
Affiliation:
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, The University of Tennessee, Knoxville, TN 37996, USA
R. R. Wilborn
Affiliation:
Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
*
†E-mail: [email protected]
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Abstract

Appetite control is a major issue in normal growth and in suboptimal growth performance settings. A number of hormones, in particular leptin, activate or inhibit orexigenic or anorexigenic neurotransmitters within the arcuate nucleus of the hypothalamus, where feed intake regulation is integrated. Examples of appetite regulatory neurotransmitters are the stimulatory neurotransmitters neuropeptide Y (NPY), agouti-related protein (AgRP), orexin and melanin-concentrating hormone and the inhibitory neurotransmitter, melanocyte-stimulating hormone (MSH). Examination of messenger RNA (using in situ hybridization and real-time PCR) and proteins (using immunohistochemistry) for these neurotransmitters in ruminants has indicated that physiological regulation occurs in response to fasting for several of these critical genes and proteins, especially AgRP and NPY. Moreover, intracerebroventricular injection of each of the four stimulatory neurotransmitters can increase feed intake in sheep and may also regulate either growth hormone, luteinizing hormone, cortisol or other hormones. In contrast, both leptin and MSH are inhibitory to feed intake in ruminants. Interestingly, the natural melanocortin-4 receptor (MC4R) antagonist, AgRP, as well as NPY can prevent the inhibition of feed intake after injection of endotoxin (to model disease suppression of appetite). Thus, knowledge of the mechanisms regulating feed intake in the hypothalamus may lead to mechanisms to increase feed intake in normal growing animals and prevent the wasting effects of severe disease in animals.

Keywords

appetiteneuropeptide Yproopiomelanocortinleptinsheep
Type
EAAP-ASAS-ADSA Growth and Development Symposium 2008
Information
animal , Volume 4 , Issue 11 , November 2010 , pp. 1781 - 1789
Copyright
Copyright © The Animal Consortium 2010

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