Dopaminergic Receptor Involvement in Insulin-Induced Anorexia in Broiler Chickens

The neurobiological mechanisms underlying appetite regulation and feeding behavior exhibit considerable complexity and interspecies variation. Among the key neurotransmitters implicated in the modulation of feeding behavior are dopamine and insulin, yet the interplay between these signaling molecules remains inadequately characterized. This investigation aimed to elucidate the interactions between insulin and the dopaminergic system in the context of appetite regulation in broiler-type chickens (Ross 308). Experimental protocols involved the intracerebroventricular (ICV) administration of insulin at doses of 2.5, 5, and 10 ng, respectively. Additionally, dopaminergic agents, including L-DOPA (a dopamine precursor) and receptor-specific antagonists SCH 23390 (D1), AMI-193 (D2), NGB 2904 (D3), and L-741,742 (D4), were administered alone or in combination with insulin (10 ng). Meal consumption was quantified cumulatively at 30-, 60-, and 120-minute intervals following the infusion. The findings revealed that insulin elicited a dose-dependent suppression of food intake (p < 0.05). Notably, the anorexigenic effect of insulin was attenuated by SCH 23390 (5 nmol) (p < 0.05), implicating D1 receptor-mediated pathways, whereas antagonists targeting D2, D3, and D4 receptors failed to modulate this response (p > 0.05). These results substantiate the critical role of D1 receptors in mediating insulin-induced anorexia in meat-type chickens, thereby advancing our understanding of the neurochemical interactions governing avian feeding behavior.