Role of orexin peptide system in emotional overeating induced by brain reward stimulation in fed rats

Introduction: The purpose of this work was to prove that the reaction of food self-deprivation in "fed up" rats is a suitable model for studying the emotional overeating in the experiment.

Methods: The self-deprivation reaction, i.e. self-isolation of an animal from food during electrical self-stimulation of the brain, was studied in animals with food deprivation. To reproduce the self-stimulation of the lateral hypothalamus, the male Wistar rats were trained to press a pedal in a Skinner box. After training, the rats received food deprivation, then a feeder was placed in the Skinner box, and a conditioned food reflex was developed in rats within 5 days.

Results and discussion: The food self-deprivation reaction was observed in the "satiated" rats with a current intensity of 10% and above the threshold for self-stimulation. Hungry animals pressed the pedal for hypothalamic self-stimulation and took no notice of the feeding trough. Sulpiride, a dopamine D2 antagonist (5 and 20 mg/kg i.p.), administered to the "satiated" rats decreased both the eating behavior and self-stimulation in food self-deprivation testing. SB-408124, an orexin A receptor antagonist (0.5 mg/ml, 20 μl intranasally) reduced only the number of pellets eaten, but not the number of pedal presses.

Conclusion: The orexin A receptors are preferably involved in emotional eating compared with orexin B (OX2R TCS-OX2-29) and D2 dopamine receptors. Because emotional eating is significantly related to clinical eating disorders, like bulimia and binge eating disorder, it seems promising to use drugs of the orexin system to treat and prevent the issue.