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The purpose of this study was to examine the effects of intracerebroventricular injection of metoprolol (a β1 adrenergic receptor antagonist), ICI 118,551 (a β2 adrenergic receptor antagonist), and SR 59230R (a β3 adrenergic receptor antagonist) on ghrelin-induced food and water intake by 3-h food-deprived (FD3) cockerels. The chickens were randomly allocated to 4 treatment groups with 8 replicates in each group. A cannula was surgically implanted into the lateral ventricle of the brain. In experiment 1, chickens received the β1 adrenergic receptor antagonist (24 nmol) before injection of the ghrelin (0.6 nmol). In experiment 2, chickens received the β2 adrenergic receptor antagonist (5 nmol) before injection of the ghrelin (0.6 nmol). In experiment 3, birds were injected with ghrelin (0.6 nmol) after the β3 adrenergic receptor antagonist (20 nmol). Cumulative food and water intake were recorded 3-h post injection and analyzed by two-way analysis of variance. According to the results, ghrelin injection reduced food and water intake by broiler cockerels (p≤0.05). The effect of ghrelin on food intake was significantly attenuated by pretreatment with the β2 receptor antagonist (p≤0.05). Furthermore, the β2 receptor antagonist had no effect on water intake induced by ghrelin. Also, pretreatment with the β1 and β3 receptors antagonists had no effect on ghrelin-induced food and water intake. These results suggest that the effect of ghrelin on cumulative food intake by cockerels is mediated via β2 adrenergic receptors.

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The present study was designed to examine the effects of intracerebroventricular injection of para-chlorophenylalanine (PCPA) (cerebral serotonin depletive), fluoxetine (selective serotonin reuptake inhibitor), 8-OH-DPAT (5-HT1A autoreceptor agonist) and SB 242084 (5-HT2c receptor antagonist) on nociceptin/orphanin FQ (N/OFQ) induced feeding response in chickens. A guide cannula was surgically implanted into the lateral ventricle of chickens. Before the experiments, 3-h fasting periods had been given to all experimental birds. In experiment 1, chickens were injected with PCPA (1.5 μg) followed by an N/OFQ injection (16 nmol) intracerebroventricularly. In experiment 2, birds received fluoxetine (10 μg) prior to the injection of N/OFQ. In experiment 3, chickens were administered with N/OFQ after the 8-OH-DPAT administration (15.25 nmol). In experiment 4, birds were injected with SB 242084 (1.5 μg) followed by an N/OFQ injection. Cumulative food intake was measured at 3 h post injection. The results of this study show that N/OFQ increases food intake in broiler cockerels (P < 0.05) and that this effect is amplified by pretreatment with PCPA and SB 242084 in an additive manner (P < 0.05). The effect of N/OFQ is not changed by pretreatment with 8-OH-DPAT (P > 0.05). Furthermore, the stimulatory effect of N/OFQ on food intake was significantly attenuated by pretreatment with fluoxetine. These results suggest that N/OFQ induced hyperphagia is mediated by serotonergic mechanisms, and possibly imply an interaction between N/OFQ and the serotonergic system (via 5-HT2C receptors) on food intake in chickens.

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