Caloric restriction increases the sensitivity to the hyperphagic effect of nociceptin/orphanin FQ limiting its ability to reduce binge eating in female rats.

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Title:	Caloric restriction increases the sensitivity to the hyperphagic effect of nociceptin/orphanin FQ limiting its ability to reduce binge eating in female rats.
Authors:	Micioni Di Bonaventura, Maria, Ubaldi, Massimo, Liberati, Sonia, Ciccocioppo, Roberto, Massi, Maurizio, Cifani, Carlo
Source:	Psychopharmacology. Jul2013, Vol. 228 Issue 1, p53-63. 11p. 1 Diagram, 3 Charts, 3 Graphs.
Subjects:	Low-calorie diet, Hyperphagia, Nociceptin, Pharmacodynamics, Psychological stress, Messenger RNA, Laboratory rats
Abstract:	Rationale: Nociceptin/orphanin FQ (N/OFQ) is a functional antagonist of corticotrophin-releasing factor, the main mediator of the stress response. Stress represents a key determinant of binge eating (BE) for highly palatable food (HPF). Objectives: In relation to the antistress properties of N/OFQ, we evaluated its effect on BE. After the observation that episodes of food restriction increase the sensitivity to its hyperphagic effects, the function of NOP receptor and N/OFQ was investigated after cycles of food restrictions. Materials and methods: In BE experiments, four groups were used: rats fed normally and not stressed or stressed, rats exposed to cycles of restriction/refeeding and then stressed, or not stressed. In the other experiments, two groups were used: rats exposed or not to food restriction. Results: Only restricted and stressed rats exhibited BE for HPF (containing chocolate cream). Intracerebroventricular injections of N/OFQ of 0.5 nmol/rat significantly reduced BE. N/OFQ 1 nmol/rat did not reduce BE but significantly increased HPF intake following food restrictions. Cycles of food restriction increased animals' sensitivity to the hyperphagic effect of N/OFQ for HPF. In situ hybridization studies following food restrictions showed decreased ppN/OFQ mRNA expression in the bed nucleus of the stria terminalis and increased expression of ppN/OFQ and NOP receptor mRNA in the ventral tegmental area and in the ventromedial hypothalamus, respectively. Conclusions: These findings indicate that N/OFQ slightly reduces BE at low doses, while higher doses increase HPF intake, due to increased sensitivity to its hyperphagic effect following a history of caloric restrictions. [ABSTRACT FROM AUTHOR]
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Database:	Psychology and Behavioral Sciences Collection

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Abstract:	Rationale: Nociceptin/orphanin FQ (N/OFQ) is a functional antagonist of corticotrophin-releasing factor, the main mediator of the stress response. Stress represents a key determinant of binge eating (BE) for highly palatable food (HPF). Objectives: In relation to the antistress properties of N/OFQ, we evaluated its effect on BE. After the observation that episodes of food restriction increase the sensitivity to its hyperphagic effects, the function of NOP receptor and N/OFQ was investigated after cycles of food restrictions. Materials and methods: In BE experiments, four groups were used: rats fed normally and not stressed or stressed, rats exposed to cycles of restriction/refeeding and then stressed, or not stressed. In the other experiments, two groups were used: rats exposed or not to food restriction. Results: Only restricted and stressed rats exhibited BE for HPF (containing chocolate cream). Intracerebroventricular injections of N/OFQ of 0.5 nmol/rat significantly reduced BE. N/OFQ 1 nmol/rat did not reduce BE but significantly increased HPF intake following food restrictions. Cycles of food restriction increased animals' sensitivity to the hyperphagic effect of N/OFQ for HPF. In situ hybridization studies following food restrictions showed decreased ppN/OFQ mRNA expression in the bed nucleus of the stria terminalis and increased expression of ppN/OFQ and NOP receptor mRNA in the ventral tegmental area and in the ventromedial hypothalamus, respectively. Conclusions: These findings indicate that N/OFQ slightly reduces BE at low doses, while higher doses increase HPF intake, due to increased sensitivity to its hyperphagic effect following a history of caloric restrictions. [ABSTRACT FROM AUTHOR]
ISSN:	00333158
DOI:	10.1007/s00213-013-3013-0