Evidence for an interaction between cannabinoidergic and dopaminergic systems with melanocortin MC۳/ MC۴ receptors in regulating food intake of neonatal chick

The current study aimed to see how the central dopaminergic and cannabinoidergic mechanisms affect melanocortin-induced food intake in the neonatal layer chickens. In this regard, ۹ experiments were designed. In experiment ۱, chicks injected with control solution, MTII (۲.۵, ۵, and ۱۰ ng). In experiment ۲, control solution, L-DOPA (۱۲۵ nmol), MTII (۱۰ ng), and L-DOPA + MTII were applied to the birds. Experiments ۳-۹ were similar to experiment ۲, except birds injected with ۶-OHDA (۱۵۰ nmol), SCH۲۳۳۹۰ (۵ nmol), AMI-۱۹۳ (۵ nmol), NGB۲۹۰۴ (۶.۴ nmol), L-۷۴۱,۷۴۲ (۶ nmol), SR۱۴۱۷۱۶A (۶.۲۵ µg), and AM۶۳۰ (۵ µg) instead of L-DOPA. Then, cumulative food intake was recorded at ۳۰, ۶۰, and ۱۲۰ min following injection. According to the results, in comparison with the control group, dose-dependent hypophagia was observed in ۳-h food-deprived neonatal layer chickens following ICV injection of MTII (۲.۵, ۵, and ۱۰ ng) (P<۰.۰۵). ICV injection of L-DOPA and SR۱۴۱۷۱۶A increased hypophagia induced by MTII in chickens (P<۰.۰۵), while ۶-OHDA greatly suppressed MTII- induced hypophagia (P<۰.۰۵). In addition, SCH۲۳۳۹۰ and AMI-۱۹۳ greatly weakened the MTII-induced hypophagia in neonatal layer chickens (P<۰.۰۵). However, NGB۲۹۰۴, L-۷۴۱۷۴۲ and AM۶۳۰ had no role on hypophagia induced by MTII (P>۰.۰۵). These results demonstrated that melanocortin-induced hypophagia in the neonatal layer chickens is likely mediated by D۱, D۲, and CB۱ receptors.

Keywords:

Dopamine , Cannabinoid , Melanocortin , food intake , Layer chicken