Assessment of the Involvement of Orexin Receptor ۱ in Acute Food Deprivation on Nociceptive Behavior Induced by Hot Plate Test in Male Rats

Background and Objective: Food deprivation increases the expression of orexin-۱ receptor gene in the hypothalamus. On the other hand, food deprivation induces analgesia and orexin has a fundamental and well known role in pain modulation. This study aimed to determine the role of orexin receptor ۱ antagonist in analgesic effect of acute food deprivation (۱۲ h) by hot plate test in male rats. Materials and Methods: Male Wistar rats were divided into ۵ groups (n=۸), control, food deprivation without surgery, stereotaxic surgery with vehicle, vehicle and food deprivation and food deprivation and orexin receptor ۱ antagonist groups. ۱۲ hours before the hot plate test, food was removed from the animals’ proximity, but water was freely available. All groups were tested using the hot plate. Data were analyzed statistically by one-way ANOVA with Tukey post hoc test. Results: According to our findings, orexin receptor ۱ antagonist injection increased pain related behaviors at the time of ۵(P<۰.۰۵), ۱۵(P<۰.۰۵), ۳۰(P<۰.۰۱) and ۶۰(P<۰.۰۰۱) minutes in the hot plate test. Conclusion: Orexin plays an important role in feeding state–induced pain modulation. Based on our results, change in pain behavior induced by food deprivation may be related to change in orexin expression or in orexin receptors density.

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Keywords: Food Deprivation , Orexin , SB-۳۳۴۸۶۷ , Hot Plate , Rat