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

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.