ABSTRACT
Title
Cycles of food restriction increase the orexigenic effect of Nociceptin/Orphanin FQ (N/OFQ) and Neuropeptide Y (NPY) in female rats
Authors
C. Cifani, MV. Micioni Di B, M. Ubaldi, R. Ciccocioppo, M. Massi
School of Pharmacy, Pharmacology Unit, University of Camerino, 62032 Camerino (MC), Italy
School of Pharmacy, Pharmacology Unit, University of Camerino, 62032 Camerino (MC), Italy
Abstract
Repeated episodes of food restriction/re-feeding, as well as stress, are known to represent key determinants of binge eating towards highly palatable food (HPF) [1]. However, the reasons accounting for the effect of food restrictions on subsequent eating behaviour is not known at present.
This study evaluated the effect of repeated cycles of food restriction/re-feeding on the hyperphagic response to the central administration of the orexigenic neuropeptides N/OFQ and NPY.
Female rats were submitted to three 8-day cycles of food restriction/re-feeding (R group). They were given for 4 days 66% of the usual chow intake, followed by 4 days of food ad libitum. Control rats (NR) had free access to food pellets for 24 days. Both groups were fed a sweet HPF for 2 h on day 5-6 and 13-14. The HPF was a paste in texture, prepared by mixing: Nutella chocolate cream (5.33 kcal/g; 56%, 31%, and 7% from carbohydrate, fat, and protein, respectively); grounded food pellets (2.6 kcal/g) and water in the following percent ratio: 52% Nutella, 33% food pellets, and 15% water. On day 25 rats received ICV injection of vehicle or of different doses of either N/OFQ or NPY.
Doses of N/OFQ in the range of 0.25-1 nmol/rat did not change HPF intake in NR rats, but significantly increased HPF intake in R rats. NPY, 0.2-0.6 µg/rat, did not stimulate HPF intake in NR rats, but elicited a significant hyperphagic response in R rats.
In situ hybridization analysis revealed significant increase in mRNA levels for the N/OFQ receptor (NOP receptor) in the ventromedial hypothalamus.
Thus, repeated food restrictions sensitize rats to the hyperphagic effect of both N/OFQ and NPY. These findings suggest that yo-yo dieting may alter the regulation of endogenous orexigenic mechanisms.
[1] Cifani et al. (2009) Psychopharmacology 204:113-25
This study evaluated the effect of repeated cycles of food restriction/re-feeding on the hyperphagic response to the central administration of the orexigenic neuropeptides N/OFQ and NPY.
Female rats were submitted to three 8-day cycles of food restriction/re-feeding (R group). They were given for 4 days 66% of the usual chow intake, followed by 4 days of food ad libitum. Control rats (NR) had free access to food pellets for 24 days. Both groups were fed a sweet HPF for 2 h on day 5-6 and 13-14. The HPF was a paste in texture, prepared by mixing: Nutella chocolate cream (5.33 kcal/g; 56%, 31%, and 7% from carbohydrate, fat, and protein, respectively); grounded food pellets (2.6 kcal/g) and water in the following percent ratio: 52% Nutella, 33% food pellets, and 15% water. On day 25 rats received ICV injection of vehicle or of different doses of either N/OFQ or NPY.
Doses of N/OFQ in the range of 0.25-1 nmol/rat did not change HPF intake in NR rats, but significantly increased HPF intake in R rats. NPY, 0.2-0.6 µg/rat, did not stimulate HPF intake in NR rats, but elicited a significant hyperphagic response in R rats.
In situ hybridization analysis revealed significant increase in mRNA levels for the N/OFQ receptor (NOP receptor) in the ventromedial hypothalamus.
Thus, repeated food restrictions sensitize rats to the hyperphagic effect of both N/OFQ and NPY. These findings suggest that yo-yo dieting may alter the regulation of endogenous orexigenic mechanisms.
[1] Cifani et al. (2009) Psychopharmacology 204:113-25