LAUSR

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 (NPY 1 , NPY 2 , and NPY 5 ) 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), NPY 1 , NPY 2 , and NPY 5 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, NPY 1 , NPY 2 , and NPY 5 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. NPY 2 receptor antagonist, resulted in increased feed intake ( p  < 0.01), while insulin, NPY 1 and NPY 5 receptors antagonist ( p  < 0.001) reduced feed intake. NPY 1 receptor antagonist, amplificated reduced effect of insulin ( p  < 0.001), and NPY 2 receptor antagonist ( p  < 0.01) demolished reduced effect of insulin on feed intake and increased it, but NPY 5 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 NPY 1 and NPY 2 receptors.