Effects of endogenous opioidergic system interaction with orexin on eating in rats

  Background: Lateral hypothalamus (LH) that produces orexin has a major role in energy homeostasis. Hypothalamic endogenous opioidergic system participates in the regulation of nutritional behaviors. There are several interactions between orexin and opioid systems.   Objective: The aim of this study was to determine the effects of endogenous opioidergic system interaction with orexin on eating in rats .   Methods: In this experimental study, 40 male rats were randomly divided into 5 equal groups: control, vehicle (saline), orexin A (30µg/rat), naloxone (30µg/rat) and naloxone and orexin A. Guide cannula was implanted by stereotaxy in the lateral ventricle of all rats. After drugs or vehicle injection into the lateral ventricle, each rat were placed into metabolic box individually and food intake, delay time for food consumption and number of approaches to food container were recorded and calculated up to 4 hours after injection. Data were analyzed using One-way ANOVA and Tukey ُ s test.   Findings: Administration of orexin A increased food intake in rats. Naloxone administration 5 min prior to orexin A injection, decreased food consumption compared to the orexin A group.   Conclusion: With regards to the results, the opioidergic system may play a role in mediating the nutritional effects of Orexin.