Food deprivation increases the mRNA expression of micro-opioid receptors in the ventral medial hypothalamus and arcuate nucleus

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2008-11, Vol.295 (5), p.R1385
• Main Authors: Barnes, Maria J, Primeaux, Stefany D, Bray, George A
• Format: Article
• Language: English
• Subjects: Animals; Arcuate Nucleus of Hypothalamus - metabolism; Dietary Fats; Eating - drug effects; Food Deprivation - physiology; Hyperalgesia - genetics; Hyperalgesia - psychology; Male; Naltrexone - analogs & derivatives; Naltrexone - pharmacology; Narcotic Antagonists - pharmacology; Rats; Rats, Long-Evans; Receptors, Opioid, delta - biosynthesis; Receptors, Opioid, delta - genetics; Receptors, Opioid, kappa - biosynthesis; Receptors, Opioid, kappa - genetics; Receptors, Opioid, mu - antagonists & inhibitors; Receptors, Opioid, mu - biosynthesis; Receptors, Opioid, mu - genetics; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; Ventromedial Hypothalamic Nucleus - metabolism
• ISSN: 0363-6119
• DOI: 10.1152/ajpregu.00030.2008

Activation of micro-opioid receptors makes animals hyperphagic and increases their preference for a high-fat diet. Previous studies have suggested that this receptor population plays a role in mediating the hyperphagia that is associated with food deprivation. In this paper, we tested the hypothesis that food deprivation will increase the expression of micro-opioid receptors in the ventral medial hypothalamus and arcuate nucleus (VMH/ARC). Food deprivation resulted in a significant increase in the mRNA expression of micro-opioid receptors in the VMH/ARC and the lateral hypothalamus (LH) after 48 h of fasting but not after 24 or 12 h of fasting in either the light or dark. We did not observe a change in the mRNA expression of kappa- or delta-opioid receptors after food deprivation. When food-deprived animals were given a choice between a low-fat diet and a high-fat diet, they were hyperphagic and consumed significantly more of the high-fat diet. When the micro-opioid receptors were blocked with beta-funaltrexamine (selective mu-opioid receptor antagonist), prior to giving food-deprived animals access to both a low-fat and high-fat diet, it significantly decreased the percentage of high-fat diet consumed. These data demonstrate that hypothalamic micro-opioid receptors may contribute to the hyperphagia and increased preference for a high-fat diet that is associated with food deprivation.