Interaction Between Central Opioidergic and Glutamatergic Systems on Food Intake in Neonatal Chicks: Role of NMDA, AMPA and mGLU1 Receptors

Abstract

The present study was designed to examine the role of opioidergic and glutamatergic systems on feeding behavior in neonatal meat-type chicken. In experiment 1, FD3 neonatal broilers ICV injected with (A) saline, (B) DAMGO (µ-opioid receptor agonist, 125 pmol), (C) MK-801 (NMDA glutamate receptors antagonist, 15 nmol) and (D) combination of DAMGO plus MK-801. Experiments 2–5 were similar to experiment 1, except FD3 chicks ICV injected with CNQX (AMPA glutamate receptors antagonist, 390 nmol), AIDA (mGLU1 receptors antagonist, 2 nmol), LY341495 (mGLU2 receptors antagonist, 150 nmol) and UBP1112 (mGLU3 receptors antagonist, 2 nmol) instead of MK-801, respectively. In experiments 6–10, FD3 chicks ICV injected as the same as procedure to the experiments 1–5, except to inject with DPDPE (δ-opioid receptor agonist, 40 nmol) instead of the DAMGO. The experiments 11–15 were similar to the experiments 1–5, except neonatal broilers ICV injected with U-50488H (κ-opioid receptor agonist, 30 nmol) instead of DAMGO. Then the cumulative food intake measured until 120 min post injection. According to the results, ICV injection of DAMGO, significantly decreased food intake (P < 0.05) while DPDPE and U-50488H increased feeding behavior compared to the control group (P < 0.05). Co-injection of the DAMGO + MK-801 and DAMGO + AIDA, significantly decreased DAMGO-induced hypophagia in neonatal chicks (P < 0.05). Also, co-injection of the DPDPE + CNQX significantly amplified DPDPE induced feeding behavior (P < 0.05). These results suggested interconnection between central opioidergic and glutamatergic systems on feeding behavior mediates via µ- and δ-opioid receptor with NMDA, AMPA and mGLU1 receptors in FD3 neonatal broilers. These findings may shed light on the circuitry underlying interconnection between central opioidergic and glutamatergic systems on feeding behavior.