Possible Involvement of Beta-Adrenergic Receptors on Nociceptin/Orphanin FQ Induced Food Consumption in Male Rats

Abstract

Background: The nociceptin/orphanin FQ (N/OFQ) peptide is the endogenous ligand for the N/OFQ peptide (NOP) receptor. Beta adrenergic receptors and N/OFQ are involved in the regulation of food intake through central and peripheral mechanisms. Objectives: The aim of this study was to determine the possible interaction between beta adrenergic and N/OFQ receptors on food consumption in male rats. N/OFQ agonists have been shown to increase food intake in mammals and birds. Beta adrenergic receptors physiologically inhibit food intake in mammals. Methods: In this experimental study were used male rats (250-300 g). In first two experiments, rats received intraperitoneal injections of isoproterenol (0, 0.5, 1 and 2 mg/kg) and Nociceptin agonist 64 - 6198 (0, 1, 2 and 4 mg/kg) respectively. In third experiment 64 - 6198 (4 mg/kg) and (2 mg/kg) isoproterenol were injected. In experiments 4 effects of isoproterenol (0.5 mg/kg) and Nociceptin antagonist (8 mg/kg) on food consumption was investigated. Latency time to feeding was examined in experiment 5. The data were statistically analyzed using One-way ANOVA and Tukey test. Results: Latency time to feeding increased and decreased by isoproterenol and nociceptin/orphanin, respectively. Administration of N/OFQ increased cumulative food intake in rats (P < 0.05). The i.p. injection of isoproterenol decreased food intake and also the hyperphagic effect of N/OFQ agonist is inhibited by isoproterenol, whereas sub-anorectic doses of isoproterenol and N/OFQ antagonist synergistically attenuated cumulative feed consumption when combined (P < 0.01). Conclusions: On the basis of these findings, it can be concluded that isoproterenol may decrease food intake in rats by reduction in the N/OFQ content.