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 ۶ experiments and each experiment had ۴ groups (ngroup=۱۱, ۵-day-old chickens). In all experiments, ۳-hour food-deprived (FD۳) 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 ۱ to ۳, ICV injections of L-arginine (precursor of NO, ۲۰۰, ۴۰۰, and ۸۰۰ nmol), L-NAME (NOS inhibitor, ۱۰۰, ۲۰۰, and ۴۰۰ nmol) and OT (۲.۵, ۵, and ۱۰ µg) were performed respectively. In experiment ۴, each group received any ICV injections of L-NAME (۱۰۰ nmol), OT (۱۰ µg) or a co-injection of L-NAME (۱۰۰ nmol) and OT (۱۰ µg). In experiment ۵, L-arginine (ICV, ۲۰۰ nmol), OT (۱۰ µg), or L-arginine (۲۰۰ nmol) and OT (۱۰ µg) were injected to the groups. Experiment ۶ was similar to the experiment ۵, although the dose of OT was ۲.۵ µg in all the treatment groups. Results showed that the ICV injection of L-NAME (۱۰۰ nmol) significantly attenuated hypophagic effect induced by OT (۱۰ µg) (p < ۰.۰۵). Findings suggested that NO might mediate the hypophagic effect of OT in FD۳ neonatal layer-type chickens. 

Keywords:

L-NAME , L-arginine , food intake , bird