| First Author | Papaleo F | Year | 2007 |
| Journal | Eur J Neurosci | Volume | 25 |
| Issue | 11 | Pages | 3398-405 |
| PubMed ID | 17553008 | Mgi Jnum | J:126072 |
| Mgi Id | MGI:3760478 | Doi | 10.1111/j.1460-9568.2007.05595.x |
| Citation | Papaleo F, et al. (2007) Decreased motivation to eat in mu-opioid receptor-deficient mice. Eur J Neurosci 25(11):3398-405 |
| abstractText | Altered motivational processes might participate to the physiopathology of eating-related disorders. The endogenous opioid system is thought to mediate the hedonic properties of food intake. To assess the role for the micro-opioid receptor (MOR) pathway in the motivational properties of food intake, in the present study we tested wild-type and MOR-deficient mice (MOR-/-) in a nose-poke operant paradigm for chow or sucrose pellets. To avoid confounding factors linked to food restriction/deprivation experience, mice were always provided with food ad libitum. Although less MOR-/- than wild-type mice initiated operant behaviour, under a fixed ratio-1 (FR-1) reinforcement schedule the two genotypes showed similar patterns of food-driven nose-poking, indicating preserved cognitive abilities in MOR-deficient mice. However, during FR-3 and progressive ratio (PR) reinforcement experiments, MOR-/- mice showed lower levels of nose-poking for either chow or sucrose pellets than wild-type mice, indicating a crucial role for the MOR pathway in the motivational properties of food intake. Moreover, under the PR reinforcement schedule mice nose-poking for sucrose pellets showed higher genotype-independent breakpoint levels than mice working for chow pellets, indicating that the MOR pathway is not essential for hedonic processing of palatable food intake. Finally, MOR-/- mice did not differ from wild-type mice in the rate of operant responding extinction, further supporting the notion of unaltered cognitive abilities in the MOR-deficient mice. The present findings strongly indicate that the MOR pathway mediates the motivational properties of food intake, but it is not essential for hedonic processing of ingestive behaviour. |
