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Appetite is controlled by a complex system of central and peripheral signals interacting to modulate the ingestion response. Several brain mediators with complex networks adjust food intake in birds. Based on the available literature, these mediators have interactions with a number of other neurotransmitters (NT S ) involved in feed intake. It means that, NT S regulate feeding behavior through mediating other peptide and NTs activity. In birds, insulin known as a hypophagic hormone that is interplaying with neuropeptide Y (NPY), pro-opiomelanocortin (POMC), and corticotropin-releasing factor (CRF) in brain. Another hormone ghrelin, inhibits food intake in birds and other mediators, such as glutamate, endocannabinoid system (ECS), serotonin (5-hydroxytryptamine, 5-HT), and norepinephrine (NE), which play a key role in ghrelin-induced hypophagia. Another involved peptide on feeding behavior in chickens called nociceptin/orphanin FQ (N/OFQ) is modulated by histamine, glutamate, dopamine (DA), gamma-aminobutyric acid (GABA), agouti-related protein (AgRP), and cocaine and amphetamine-regulated transcript (CART). Some of the NT S such as opioid have both orexigenic and anorexigenic effects in birds while has interaction with NE, glutamate, histamine, DA, and cannabinoids (CBs). Thus, interaction among mediators is a prominent process needs to be considered in order to understanding the mechanisms underlying feed intake regulation in birds. This review aims to investigate the role of major regulators and their mediatory interactions with one another in poultry feeding behavior. According to mentioned interactions, it seems that dopamine, serotonin, and glutamate have the most interactions with other NT systems. Therefore, they play an axial role in the central regulation of food intake in CNS.

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1. Serotoninergic and adrenergic systems play crucial roles in feed intake regulation in avians but there is no report on possible interactions among them. So, in this study, 5 experiments were designed to evaluate the interaction of central serotonergic and adrenergic systems on food intake regulation in 3 h food deprived (FD) neonatal layer-type chickens. 2. In Experiment 1, chickens received intracerebroventricular (ICV) injection of control solution, serotonin (56.74 nmol), prazosin (α receptor antagonist, 10 nmol) and co-injection of serotonin plus prazosin. In Experiment 2, control solution, serotonin (56.74 nmol), yohimbine (α receptor antagonist, 13 nmol) and co-injection of serotonin plus yohimbine were used. In Experiment 3, the birds received control solution, serotonin (56.74 nmol), metoprolol (β receptor antagonist, 24 nmol) and co-injection of serotonin plus metoprolol. In Experiment 4, injections were control solution, serotonin (56.74 nmol), ICI 118.551 (β receptor antagonist, 5 nmol) and serotonin plus ICI 118.551. In Experiment 5, control solution, serotonin (56.74 nmol), SR59230R (β receptor antagonist, 20 nmol) and co-administration of serotonin and SR59230R were injected. In all experiments the cumulative food intake was measured until 120 min post injection. 3. The results showed that ICV injection of serotonin alone decreased food intake in chickens. A combined injection of serotonin plus ICI 118.551 significantly attenuated serotonin-induced hypophagia. Also, co-administration of serotonin and yohimbine significantly amplified the hypophagic effect of serotonin. However, prazosin, metoprolol and SR59230R had no effect on serotonin-induced hypophagia in chickens. 4. These results suggest that serotonin-induced feeding behaviour is probably mediated via α and β adrenergic receptors in neonatal layer-type chicken.