Intracerebroventricular injection of orexin-A, but not orexin-B, induces arousal of layer-type neonatal chicks.

In order to determine if orexins affect arousal in neonatal chicks, we intracerebroventricularly (ICV) injected either orexin-A or orexin-B to layer and broiler type chicks (Gallus gallus) and measured their behaviors and food intake following injection. Layer chicks treated with orexin-A at 0.2 and 2.0 nmol had increased arousal but their food intake was not affected. However, arousal was not affected in broiler chicks treated with orexin-A, but they spent less time feeding. When orexin-B was administered to layer and broiler chicks, neither had altered arousal and their food intake was not affected. Therefore, the orexin peptides may differentially affect arousal in the two stocks tested; orexin-A causes a stock dependant increase whereas orexin-B does not affect either.