Some neuropeptides such as neuropeptide Y -NPY- maintain energy balance. The aim of this study was to investigate the role of insulin on feed intake and their interaction with NPY receptors -NPY1, NPY2, and NPY5- in newly hatched chickens -5-day-old chickens-. This study was performed in 7 experiments -in each experiment, 4 groups with 6 replications-. In the first 4 experiments were used to investigate the doses of insulin -2.5, 5 and 10 ng-, NPY1, NPY2, and NPY5 receptors antagonist -1.25, 2.5 and 5 μg- on feed intake via intraventricular injection were evaluated, as well as effective and sub-effective doses were determined. After that, the interactions of these compounds with insulin were investigated in 3 experiments. In experiments 5, 6 and 7, chickens received, NPY1, NPY2, and NPY5 receptors antagonist, prior to injection of insulin, respectively; then the chicken was injected with insulin to study the feed intake. In each experiment, the control group received a control solution. Then, in each experiment cumulative feed intake were measured up to 120 min after injection. NPY2 receptor antagonist, resulted in increased feed intake -p < 0.01-, while insulin, NPY1 and NPY5 receptors antagonist -p < 0.001- reduced feed intake. NPY1 receptor antagonist, amplificated reduced effect of insulin -p < 0.001-, and NPY2 receptor antagonist -p < 0.01- demolished reduced effect of insulin on feed intake and increased it, but NPY5 receptor antagonist did not affect hypophagic effect of insulin -p > 0.05-. It is concluded that, insulin has a decreasing effect on newly hatched chicken’s feed intake via NPY1 and NPY2 receptors.

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