Interconnection between Adrenergic and Dopaminergic Systems in Feeding Behavior in Neonatal Chicks

Central dopaminergic (DAergic) and adrenergic systems have a prominent role in appetite regulation; however, their interaction(s) have not been studied in neonatal layer chickens.Therefore, the current study aimed to determine the interaction of central DAergic and noradrenergic systems in food intake regulation in neonatal layer chickens. In the first experiment, chickens received the intracerebroventricular (ICV) injection of a control solution, prazosin (i.e., α۱ adrenergic receptor antagonist; ۱۰ nmol), dopamine (DA; ۴۰ nmol), and prazosin plus DA. The second to fifth experiments were similar to the first experiment except that the birds were injected with yohimbine (i.e., α۲ receptor antagonist; ۱۳ nmol), metoprolol (i.e., β۱ adrenergic receptor antagonist; ۲۴ nmol), ICI ۱۱۸,۵۵۱ (i.e., β۲ adrenergic receptor antagonist; ۵ nmol), and SR۵۹۲۳۰R (i.e., β۳ adrenergic receptor antagonist; ۲۰ nmol) instead of prazosin. In the sixth experiment, the chickens received ICV injection with the control solution and noradrenaline (NA; ۷۵, ۱۵۰, and ۳۰۰ nmol). In the seventh experiment, the birds were injected with the control solution, SCH۲۳۳۹۰ (i.e., D۱ DAergic receptor antagonist; ۵ nmol), NA (۳۰۰ nmol), and SCH۲۳۳۹۰ plus NA In the eighth experiment, the control solution, AMI-۱۹۳ (i.e., D۲ DAergic receptor antagonist; ۵ nmol), NA (۳۰۰ nmol), and AMI-۱۹۳ plus NA were injected. Then, cumulative food intake was recorded at ۳۰, ۶۰, and ۱۲۰ min after the injection. According to the obtained results, the ICV injection of DA (۴۰ nmol) significantly decreased food intake in comparison to that reported for the control group (p <۰.۰۵). The co-injection of yohimbine plus DA significantly amplified DA-induced hypophagia in the neonatal chickens (p <۰.۰۵). In addition, the co-administration of ICI ۱۱۸,۵۵۱ plus DA significantly inhibited the hypophagic effect of DA in the neonatal chickens (p <۰.۰۵). Furthermore, NA (۷۵, ۱۵۰, and ۳۰۰ nmol) significantly reduced food intake in a dose-dependent manner (p <۰.۰۵). The co-injection of SCH۲۳۳۹۰ plus NA decreased the hypophagic effect of NA in the neonatal chickens, compared to that reported for the control group (p <۰.۰۵). The co-injection of AMI-۱۹۳ plus NA diminished NA-induced hypophagia, compared to that reported for the control group (p <۰.۰۵). The aforementioned results suggested that there is an interconnection between central DAergic and noradrenergic systems through α۲/β۲ adrenergic and D۱/D۲ DAergic receptors in food intake regulation in neonatal chicks.

کلیدواژه ها:

Adrenergic ، Dopamine ، Food intake ، Layer chicken