Effect of Centrally Administered Neuropeptide Y and α-Melanocyte-stimulating Hormone on Water Intake in Chicks

From an animal welfare perspective, thirst avoidance is an important criterion for the poultry industry. Neuropeptide Y (NPY) and α-melanocyte-stimulating hormone (α-MSH) play critical roles in regulating food intake, which is closely related to water intake in mammals and chickens. This study aimed to clarify the role of appetite-regulating neuropeptides in controlling thirst in chicks. In Experiment 1, 7-day-old male chicks were allocated to two groups and deprived of water for 24 h. Chicks were intracerebroventricularly injected with saline or the peptide. Water intake was measured at 60 and 120 min after injection under feed-deprived conditions. α-MSH significantly suppressed thirst-induced water intake, whereas NPY exhibited no effect. In Experiment 2, 8-day-old male chicks were allocated to two groups and intracerebroventricularly injected with either saline or peptide under <i>ad libitum</i> drinking conditions. NPY significantly increased water intake, whereas α-MSH had no effect. In Experiment 3, 8-day-old male chicks were allocated to two groups and euthanized after 0 or 3 h of water deprivation. Diencephalon mRNA levels of <i>NPY</i> and proopiomelanocortin (the gene encoding α-MSH) were not affected by water deprivation. Our findings suggest that chick NPY and α-MSH function as thirst-inducing and thirst-quenching peptides, respectively. Both control water intake through post-translational regulation.