Interaction Between Oxytocin and Opioidergic System on Food Intake Regulation in Neonatal Layer Type Chicken

Abstract

The aim of the current study was to determine possible interaction of central oxytocin and opioidergic system on food intake regulation in neonatal layer-type chicken. In experiment 1, FD3 chicken ICV injected with control solution, oxytocin (10 µg), β-FNA (µ receptor antagonist, 5 µg) and oxytocin (10 µg) + β-FNA were injected. Experiments 2–6 were similar to experiments 1, except chicken injected with nor-BNI (κ receptor antagonist, 5 µg), NTI (δ receptor antagonist, 5 µg), DAMGO (µ receptor agonist, 62.25 pmol), U-50488H (κ receptor agonist, 10 nmol), DPDPE (δ receptor agonist, 20 pmol) instead of β-FNA. In experiment 7, control solution, DAMGO (125 pmol), d(CH2)5Tyr(Me)-[Orn8]-vasotocin (oxytocin antagonist, 5 µg) and DAMGO + d(CH2)5Tyr(Me)-[Orn8]-vasotocin were ICV injected to FD3 chicken. Experiments 8 and 9 were similar to experiments 7, except chicken injected with U-50488H (30 nmol) and DPDPE (40 pmol) instead of DAMGO. Then, cumulative food intake was recorded at 30, 60 and 120 min after injection. According to the results, ICV injection of the oxytocin (10 µg) significantly decreased food intake compared to control group (P < 0.05). Co-injection of the oxytocin + β-FNA and oxytocin + U-50488H significantly decreased hypophagic effect of the oxytocin (P < 0.05). While, co-injection of the oxytocin + nor-BNI or oxytocin + DAMGO significantly amplified hypophagic effect of the oxytocin in chicken (P < 0.05). In addition, ICV injection of DAMGO (125 pmol) significantly decreased cumulative food intake compared to control group (P < 0.05). However, co-addministration of the DAMGO + (CH2)5Tyr(Me)-[Orn8]-vasotocin significantly decreased hypophagic effect of the DAMGO (P < 0.05) in chicken. These results suggested there are interconnection between oxytocin and opioidergic system on central food intake regulation, which mediates via µ and κ opioidergic receptors in neonatal layer-type chicken.