A newly discovered interference of the central nitrergic system on oxytocin-induced hypophagia in layer-type chickens

Various neurochemical pathways are participating in the regulation of food intake in mammals and birds. Both oxytocin (OT) and nitric oxide (NO) are known as hypophagic agents in birds.  This study consisted of 6 experiments and each experiment had 4 groups (ngroup=11, 5-day-old chickens). In all experiments, 3-hour food-deprived (FD3) birds received intracerebroventricular (ICV) injections either control diluent or drug solution. Then the birds had ad libitum access to the food and fresh water and then cumulative food intake (gr) was measured based on the percentage of the body weight (%BW). In experiments 1 to 3, ICV injections of L-arginine (precursor of NO, 200, 400, and 800 nmol), L-NAME (NOS inhibitor, 100, 200, and 400 nmol) and OT (2.5, 5, and 10 µg) were performed respectively. In experiment 4, each group received any ICV injections of L-NAME (100 nmol), OT (10 µg) or a co-injection of L-NAME (100 nmol) and OT (10 µg). In experiment 5, L-arginine (ICV, 200 nmol), OT (10 µg), or L-arginine (200 nmol) and OT (10 µg) were injected to the groups. Experiment 6 was similar to the experiment 5, although the dose of OT was 2.5 µg in all the treatment groups. Results showed that the ICV injection of L-NAME (100 nmol) significantly attenuated hypophagic effect induced by OT (10 µg) (p < 0.05). Findings suggested that NO might mediate the hypophagic effect of OT in FD3 neonatal layer-type chickens.