Possible effects of the central adrenergic and dopaminergic receptors on hypophagia induced by neuromedin S in neonatal layer-type chicks.

The current study was aimed to determine the possible effects of the central adrenergic and dopaminergic receptors in neuromedin S (NMS)-induced hypophagia in neonatal layer-type chickens. In the first experiment, control solution, and NMS (0.25, 0.5, and 1 nmol), were injected (intracerebroventricular (ICV)) in chickens. In the second experiment, birds were injected with a control solution,SCH23390 (Dreceptor antagonist, 5 nmol), NMS (1 nmol), and a combination of the SCH23390 + NMS. Experiments 3-11 were similar to experiment 2, except that chickens were injected withAMI-193 (Dreceptor antagonist, 5 nmol), NGB2904(Dreceptor antagonist, 6.4 nmol), L-741,742(Dreceptor antagonist, 6 nmol), 6-OHDA(6-hydroxydopamine, 2.5 nmol),Prazosin(αreceptor antagonist, 10 nmol),Yohimbine(αreceptor antagonist, 13 nmol),Metoprolol(βreceptor antagonist receptor, 24 nmol),ICI 118,551 (βreceptor antagonist, 5 nmol),SR 59230R (β receptor antagonist, 20 nmol) instead ofSCH23390. Then, cumulative food intake was recorded at 30, 60, and 120 min following the injection. According to the results, food intake was significantly decreased after ICV injection of NMS in a dose -dependent manner (P < 0.05). Also, the co-injection of the SCH23390 + NMS significantly attenuated NMS-induced hypophagia (P < 0.05). The co-administration of AMI-193 + NMS significantly reduced NMS- induced hypophagia (P < 0.05). In addition, the co-injection of ICI 118,551 + NMS and 6-OHDA + NMS considerably decreased NMS-induced food consumption (P < 0.05). However, NGB2904, L-741742, Prazosin, Yohimbine, Metoprolol and SR 59230R had no effect on hypophagia induced by NMS (P > 0.05). These results demonstrated thatNMS- induced hypophagia might be mediated by D/D dopaminergic andβadrenergic receptors in neonatal layer-type chickens.