THE MELANOCORTIN SYSTEM
Copyright © 2003 by the New York Academy of Sciences
description
Annals of the New York Academy of Sciences 994:187-191 (2003)
© 2003 New York Academy of Sciences
Agouti-Related Protein: Appetite or Reward?
PAWEL K. OLSZEWSKIa,b,c,
KATHIE WICKWIREd,
MICHELLE M. WIRTHe,
ALLEN S. LEVINEa,b,f AND
SILVIA Q. GIRAUDOd
aResearch Service, Veterans Affairs Medical Center, Minneapolis, Minnesota 55417, USA
bDepartment of Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA
cUniversity of Minnesota College of Veterinary Medicine, St. Paul, Minnesota 55108, USA
dDepartment of Foods and Nutrition, University of Georgia, Athens, Georgia 30602, USA
eDepartment of Psychology, University of Michigan, Ann Harbor, Michigan 48109, USA
fDepartment of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota 55108, USA
Address for correspondence: Silvia Q. Giraudo, Department of Foods and Nutrition, University of Georgia, Athens, GA 30602. Voice: 706-542-697; fax: 706-542-5059.
sgiraudo{at}uga.edu
Ann. N.Y. Acad. Sci. 994: 187-191 (2003).
Agouti-related protein (AgRP) is an orexigenic peptide that acts as an antagonist of the melanocortin-3 and -4 receptors in the hypothalamus. Studies suggest that the melanocortin and opioid systems interact in the control of ingestive behavior. Also, AgRP has been shown to especially increase intake of a palatable diet. Given these observations, we wished to examine whether the effects of AgRP on ingestive behavior resemble those of opioids. AgRP was injected into the hypothalamic paraventricular nucleus in animals given a choice between a palatable sucrose solution and calorically dense chow. As a result of AgRP injection, animals increased intake of chow but not sucrose relative to controls, in contrast to what has been seen with opioid agonists. These results together with prior findings suggest that the primary effect of AgRP is to cause an increase in food intake to satisfy energy needs, though AgRP also has opioid-like effects, possibly due to melanocortin-opioid interactions.
Key Words: agouti-related protein (AgRP) • melanocortins • opioids • paraventricular nucleus (PVN) • food intake
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