Central administration of galanin-like peptide (GALP) causes short-term orexigenic effects in broilers: Mediatory role of NPY1 and D1 receptors.

Studies conducted on mammalian models have indicated the role of galanin-like peptide (GALP) in appetite regulation. For the first time, the present study examines the effects of this peptide on feed consumption and behavioral changes, as well as its interaction with dopaminergic and neuropeptide Y (NPY) systems in broilers. In experiment 1, broilers were injected with GALP (0.5, 1, and 2 μg) and saline. In experiment 2, saline, NPY1 receptor antagonist (BIBO-3304), GALP (2 μg), and BIBO-3304 + GALP were administrated. Experiments 3-6 were identical to experiment 2, except that NPY2 receptor antagonist (BIIE 0246), NPY5 receptor antagonist (CGP 71683A), D1 receptor antagonist (SCH39166), and D2 receptor antagonist (L-741,626) were injected instead of BIBO-3304. After that, cumulative meal consumption was recorded for 2 h. Also, behavioral changes in the broilers receiving GALP (0.5, 1, and 2 μg) were monitored for thirty minutes after infusion. Following the administration of GALP (1 and 2 μg), food intake and the number of feeding and exploratory pecks of chicks increased (P < 0.05), while other behaviors did not change significantly (P ≤ 0.05). Co-infusion of BIBO-3304 + GALP suppressed the orexigenic effect of GALP (P < 0.05). Infusion of BIIE 0246, CGP 71683A, and L-741,626 with GALP, had no significant effect on GALP-induced hyperphagia (P ≤ 0.05). However, the orexigenic effects of GALP were stimulated following the co-administration of SCH39166A + GALP (P < 0.05). These findings indicate that NPY1 and D1 receptors can mediate GALP-induced hyperphagia in broilers.