Sweet taste pleasantness is modulated by morphine and naltrexone

Eikemo, M., Løseth, G. E., Johnstone, T., Gjerstad, J., Frode, W. and Leknes, S. (2016) Sweet taste pleasantness is modulated by morphine and naltrexone. Psychopharmacology, 233 (21). pp. 3711-3723. ISSN 1432-2072 doi: 10.1007/s00213-016-4403-x

Abstract/Summary

Rodent models highlight the key role of µ-opioid receptor (MOR) signaling in palatable food consumption. In humans however, the effects of MOR stimulation on eating and food liking remain unclear. In a bidirectional psychopharmacological cross-over study, 49 healthy men underwent a sweet taste paradigm following double-blind administration of the MOR agonist morphine, placebo, and the opioid antagonist nalt rexone. We hypothesized that behaviors regulated by the endogenous MOR system would be enhanced by MOR agonism, and decreased by antagonism. The strongest drug effects were expected for the sweetest (high-calorie) sucrose solution, as reported in rodents. However, very sweet sucrose-water solutions are considered sickly and aversive by many people (called sweet dislikers). Since both sweet likers and dislikers were tested, we were able to assess whether MOR manipulations affect pleasantness ratings differently depending on both subjective and objective value. As hypothesized, MOR stimulation with morphine increased pleasantness of the sweetest of five sucrose solutions, without enhancing pleasantness of the lower-sucrose solutions. For opioid antagonism, an opposite pattern was observed for the sweetest drink only. This bidirectional effect of agonist and antagonist treatment is consistent with rodent findings that MOR manipulations most strongly affect the highest-calorie foods. Importantly, the observed drug effects on pleasantness of the sweetest drink did not differ between sweet likers and dislikers. We speculate that the MOR system promotes survival in part by increasing concordance between the objective (caloric) and subjective (hedonic) value of food stimuli, so that feeding behaviour becomes more focused on the richest food available.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/66299
Item Type	Article
Refereed	Yes
Divisions	Interdisciplinary Research Centres (IDRCs) > Centre for Integrative Neuroscience and Neurodynamics (CINN) Life Sciences > School of Psychology and Clinical Language Sciences > Department of Psychology Life Sciences > School of Psychology and Clinical Language Sciences > Neuroscience Life Sciences > School of Psychology and Clinical Language Sciences > Psychopathology and Affective Neuroscience
Publisher	Springer Verlag
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