Interaction between central cholecystokinin and dopaminergic system in layer-type chickens' food intake.

The mechanisms governing food intake and appetite regulation in the brain are intricate and vary across different animal species. Dopamine and cholecystokinin (CCK) are recognized as two critical neurotransmitters involved in the control of food intake; however, the potential interactions between these neurotransmitters remain poorly understood. Consequently, this study aimed to investigate the interactions between central CCK and the dopaminergic system in the feeding behavior of layer-type chickens. In this experiment, birds were administered intracerebroventricular (ICV) injections of CCK4, CCK8, and CCK8s at doses of 0.25, 0.5, and 1 nmol, respectively. Additionally, various compounds were injected ICV, including L-DOPA (a dopamine precursor), 6-OHDA (a dopamine synthesis inhibitor), SCH 23390 (a D1 receptor antagonist), AMI-193 (a D2 receptor antagonist), NGB 2904 (a D3 receptor antagonist), and L-741,742 (a D4 receptor antagonist), either alone or in combination with CCK8s (1 nmol). The cumulative feed consumption was measured at 30, 60, and 120 minutes following the injections. The results indicated that ICV administration of CCK4 and CCK8 did not significantly influence feeding behavior (P ≥ 0.05). In contrast, CCK8s at a dose of 1 nmol resulted in a dose-dependent reduction in feed consumption (P < 0.05). Furthermore, SCH 23390 (5 nmol) and 6-OHDA (150 nmol) mitigated the inhibitory effect of CCK8s on feed consumption (P < 0.05), whereas NGB2904 (6.4 nmol), AMI-193 (5 nmol), and L-741,742 (6 nmol) did not exhibit significant effects (P ≥ 0.05). This study substantiates the involvement of D1 receptors in the hypophagic response induced by CCK8s in layer-type chickens.