Complexity of neural mechanisms underlying overconsumption of sugar in scheduled feeding: Involvement of opioids, orexin, oxytocin and NPY

Pawel K. Olszewski, Timothy J. Shaw, Martha K. Grace, Catherine E. Höglund, Robert Fredriksson, Helgi B. Schiöth, Allen S Levine

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

A regular daily meal regimen, as opposed to ad libitum consumption, enforces eating at a predefined time and within a short timeframe. Hence, it is important to study food intake regulation in animal feeding models that somewhat reflect this pattern. We investigated the effect of scheduled feeding on the intake of a palatable, high-sugar diet in rats and attempted to define central mechanisms - especially those related to opioid signaling - responsible for overeating sweet foods under such conditions. We found that scheduled access to food, even as challenging as 20 min per day, does not prevent overconsumption of a high-sucrose diet compared to a standard one. An opioid receptor antagonist, naloxone, at 0.3-1 mg/kg b. wt., decreased the intake of the sweet diet, whereas higher doses were required to reduce bland food consumption. Real-time PCR analysis revealed that expression of hypothalamic and brainstem genes encoding opioid peptides and receptors did not differ in sucrose versus regular diet-fed rats, which suggests that scheduled intake of sweet food produces only a transient change in the opioid tone. Intake of sugar was also associated with upregulation of orexin and oxytocin genes in the hypothalamus and NPY in the brainstem. We conclude that scheduled consumption of sugar diets is associated with activity of a complex network of neuroregulators involving opioids, orexin, oxytocin and NPY.

Original languageEnglish (US)
Pages (from-to)226-233
Number of pages8
JournalPeptides
Volume30
Issue number2
DOIs
StatePublished - Feb 2009

Bibliographical note

Funding Information:
This research was supported in part by the National Institute of Drug Abuse (R01DA021280), the National Institute of Diabetes and Digestive and Kidney Diseases (P30 DK50456) and the Swedish Research Council and Åhlens foundation.

Keywords

  • Deprivation
  • Diet
  • Obesity
  • Peptides
  • Rats
  • Restriction
  • Reward

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