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.