Dopamine- induced hypophagia is mediated via NMDA and mGlu1 receptors in chicken

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.