Role of nitrergic systems in feed intake induced by nociceptin/orphanin FQ in neonatal meat-type chickens

Various neurochemical pathways participate in regulating food intake in mammals and birds. The nociceptin/orphanin FQ ‎(N/OFQ) ‎is involved in the central nervous system and increass food intake. Nitric oxide (NO) is a hypophagic agent in birds. ‎The present study aimed to investigate the central nociceptin/orphanin FQ (N/OFQ) effects and its interaction with nitrergic systems on feeding behavior in neonatal chickens.

Seventy-two neonatal male broiler-type (Ross 308) chickens were divided randomly into two experimental groups. Each experiment had a control group and three treatment groups (n = 12). In all experiments, 3-hour food-deprived (FD3) birds received intracerebroventricular (ICV) ‎injections either diluent (control) or drug solution. Then the birds had ad libitum access to the ‎food and fresh water, and then cumulative food intake (g) was measured based on the ‎percentage of the body. In the first experiment, chickens received ICV injection of L-arginine (NO precursor, 400 nmol), N/‎OFQ (16 nmol), and L-arginine with N/OFQ. L-NAME (NO ‎synthase inhibitor, 200 nmol), N/OFQ (16 nmol), and L-NAME + N/‎OFQ were injected in the second experiment.‎

ICV injection of N/OFQ significantly increased food intake (p < 0.05). Injection of the N/OFQ + L-arginine significantly attenuated the hyperphagic effect induced by N/OFQ in neonatal broilers (p < 0.05). Conversely, injection of the N/OFQ + L-NAME significantly decreased the hyperphagic effect induced by N/OFQ (p < 0.05).

Our findings suggest that the hyperphagic effect of central N/OFQ ‎ in FD3 neonatal layer-type ‎chicken is probably mediated by nitric oxide.‎