BACKGROUND: Brain monoamines (such as histamine and dopamine) play an important role in emotions, cognition, reward and feeding behavior. The interactions between histamine and dopamine were studied in many physiological functions but this correlation is unclear in feeding behavior of chickens. The aim of this study was to investigate the interaction of central histaminergic and dopaminergic systems on food intake in broiler chicken. METHODS: In this study we used from intracerebroventricular (ICV) injection for manipulating of histaminergic and dopaminergic systems. In Experiment 1, 3 h-fasted chicks were given an ICV injection of histamine, SCH23390, a D1 receptors antagonist and co-injection of histamine and SCH23390. Experiments 2-5 were similar to experiment 1 except birds were injected with AMI-193, D2 receptors antagonist; NGB2904, D3 receptors antagonist; L-741,742, D4 receptors antagonist and 6-OHDA, 6-hydroxydopamine instead of SCH 23390, respectively. In experiment 6, ICV injection of dopamine, chlorpheniramine, H1 receptors antagonist and co-administration of dopamine and chlorpheniramine were done. Experiments 7-9 were similar to experiment 6, except birds ICV injected with famotidine, H2 receptors antagonist; thioperamide, H3 receptors antagonist and α-FMH, alpha-fluoromethylhistidine in place of chlorpheniramine, respectively. Then cumulative food intake (g) was measured at 30, 60 and 120 min after the injection. RESULTS: Histamine decreased food intake compared to the control chicks indicating a inhibitory effect of histamine on food intake and SCH23390 attenuated the effect of histamine on food intake(P<0.001). In addition, hypophagic effect of histamine decreased by 6-OHDA(P<0.001). Chlorpheniramine and α-FMH significantly attenuated dopamine induced hypophagia(P<0.001). However, thioperamide amplified the inhibitory effect of dopamine on food intake(P<0.001). CONCLUSIONS: These results suggest, there is relationship between histaminergic and dopaminergic systems on food intake in chicken and H1, H3 and D1 receptors are involved in this interaction.

Background: Feeding behavior is regulated by a complex network which interacts via diverse signals from central and peripheral tissues. It is known dopaminergic and glutamatergic systems have crucial role on food intake regulation but scarce reports exist on their interaction in appetite regulation in broilers. OBJECTIVES: The present study was designed to examine the role of glutamatergic system on dopamine-induced hypophagia in neonatal meat-type chicken. METHODS: In experiment 1, chicks received ICV injection of control solution, dopamine (40 nmol), MK-801 (NMDA glutamate receptors antagonist, 15 nmol) and co-injection of dopamine + MK-801. In experiment 2, birds were ICV injected with saline, dopamine (40 nmol), CNQX (AMPA glutamate receptors antagonist, 390 nmol) and co-injection of dopamine + CNQX. In experiment 3, chicks received ICV injection of control solution, dopamine (40 nmol), AIDA (mGLUR1 glutamate receptors antagonist, 2 nmol), dopamine + AIDA. Experiments 4 and 5 were similar to experiment 3, except birds were injected with LY341495 (mGLUR2 glutamate receptors antagonist, 150 nmol) and UBP1112 (mGLUR3 glutamate receptors antagonist, 2 nmol) instead of AIDA. Then the cumulative food intake was measured until 120 min post injection. RESULTS: According to the results, ICV injection of dopamine significantly decreased food intake (p<0.001). Co-injection of dopamine and MK-801 decreased dopamine induced hypophagia (p<0.001). Moreover, the food intake of chicks was significantly increased by co-injection of AIDA and dopamine (p<0.001). CONCLUSIONS: These results suggest dopamine-induced hypophagia is mediated via NMDA and mGlu1 receptors in chicken.