Exogenous prolactin-releasing peptide's orexigenic effect is associated with hypothalamic neuropeptide Y in chicks

• Chicks that received central injections of PrRP dose-dependently increased food intake with a dose as low as 3 pmol.
• Central PrRP injection did not affect water intake.
• Hypothalamic neuropeptide Y mRNA was increased in centrally injected PrRP chicks.

Exogenous administration of prolactin-releasing peptide (PrRP) exerts anorexigenic effects in rats while causing orexigenic effects in chicks. While the central mechanism mediating PrRP's effect on food intake in rodents is somewhat understood, in chicks information is lacking. Therefore, this study was designed to elucidate the hypothalamic mechanism of PrRP induction of hunger perception in chicks. Chicks that received intracerebroventricular (ICV) injections of PrRP dose-dependently increased their food intake with no effect on water intake or whole blood glucose concentration. The threshold of food intake stimulation was as low as 3 pmol, thus as compared to other neuropeptides PrRP is exceptionally potent. The mRNA abundance of several appetite-associated neuropeptide genes was quantified and hypothalamic neuropeptide Y (NPY) mRNA was increased in PrRP-injected chicks. Therefore, the orexigenic effects of PrRP may be associated with increased NPY-ergic tone. These results provide insight into the evolutionary aspects of appetite regulation during the course of divergent evolution of mammals and birds.