Synergistic Effect of Oxytocin with mu Opioid Receptor Agonist on Central Control of Food Intake in neonatal Chickens

The opioidergic system and its different receptors play an important role in the central control of food intake in birds. On the other hand, the decreasing effect of oxytocin on food intake of birds has been observed. The present study was conducted to investigate the synergistic effects of oxytocin with opioid receptors on food intake in neonatal layer chickens.

In this study, three experiments were designed, so that each experiment included one control group and three treatment groups. In all groups, birds received intracerebroventricular injection of diluent solution or drug solution after 3 hours of food deprivation. In the first experiment, normal saline, oxytocin(0.16 nmol), DAMGO(62.5 picomol) (agonist of mu-opioid receptors) and oxytocin plus DAMGO were injected. The other experiments were conducted as experiment 1, but instead of DAMGO, DPDPE (20 nmol)(agonist of delta opioid receptors) in the experiment 2 and U-50488H (10 nmol)(agonist of kappa opioid receptors) in experiment 3 were injected either alone or in combination with oxytocin. After the injection, water and food were freely available to the birds and then cumulative food intake (gr) was measured based on the ‎percentage of the body weight.

The results of the present study showed that sub effective dose injection of oxytocin plus DAMGO significantly reduced food intake in layer chickens (P<0.05).

According to the results of the present study, there is probably a synergistic effect between oxytocin with mu-opioid receptors agonist on food intake control of neonatal layer chicks.