The information emerging from the studies demonstrates adrenergic system and nociceptin/orphanin FQ (N/OFQ) play a crucial role on appetite regulation but there is no information for their interaction. The purpose of this study was to examine the effects of intracerebroventricular (ICV) injection of prazosin (a 1 receptor antagonist), yohimbine (a 2 receptor antagonist), metoprolol (b 1 adrenergic receptor antagonist), ICI 118,551 (b 2 adrenergic receptor antagonist) and SR59230R (b 3 adrenergic receptor antagonist) on N/OFQ-induced hyperphagia by 3-h fooddeprived neonatal broiler chicken. In experiment 1, chicken injected with saline, prazosin (10 nmol), N/OFQ (16 nmol) and co-injection of prazosin ? N/OFQ. In experiment 2, ICV injection of saline, yohimbine (13 nmol), N/OFQ (16 nmol) and yohimbine ? N/OFQ applied to the birds. In experiment 3, injections were saline, metoprolol (24 nmol), N/OFQ (16 nmol) and metoprolol ? N/OFQ. In experiment 4, the birds received ICV injection of saline, ICI 118,551 (5 nmol), (C) N/OFQ (16 nmol) and co-administration of ICI 118,551 ? N/OFQ. In experiment 5, chicken injected with saline, SR59230R (20 nmol), N/OFQ (16 nmol) and SR59230R ? N/OFQ. Then, cumulative food intake was recorded until 120 min after injection.According to the results, ICV injection of N/OFQ significantly increased food intake (P \ 0.001). The effect of N/OFQ significantly amplified by co-injection of N/OFQ ? b 2 adrenergic receptor antagonist (P \ 0.001). Also, administration of b 1 or b 3 adrenergic receptor antagonist had no effect on N/OFQ-induced hyperphagia (P [ 0.05). These results suggest that the effect of N/OFQ on cumulative food intake is mediated via b 2 adrenergic receptors in neonatal chicken.