Interaction of Central Glutamatergic and Histaminergic Systems on Food Intake Regulation in Layer Chickens

This study purposed to discover the connection between the central glutamatergic and histaminergic systems on feeding behavior in layer chickens. In the first experiment, chicks obtained intracerebroventricular (ICV) injections of saline (control solution), α-FMH (250 nmol), glutamate (300 nmol), and α-FMH + glutamate. Experiments 2-6 were comparable to the first experiment, apart from the birds being injected with chlorpheniramine (histamine H₁ receptor antagonist, 300 nmol), famotidine (histamine H₂ receptor antagonist, 82 nmol), and thioperamide (histamine H3 receptor antagonist, 300 nmol) instead of α-FMH. In Experiment five, experimental groups were divided into (A) control solution, (B) MK-801 (N-methyl-D-aspartate receptor antagonist, 15 nmol), (C) histamine (300 nmol) and (D) MK-801 + histamine. Experiments 6-10 and Experiment five were similar apart from the ICV injections of CNQX (AMPA receptor antagonist, 360 nm), UBP-302 (Kainate receptor antagonist, 390 nm), AIDA (mGluR₁ antagonist, 2 nmol), LY341495 (mGluR₂ antagonist, 150 nmol), and UBP1112 (mGluR₃ antagonist, 2 nmol) given instead of MK-801. Afterward, cumulative food intake was recorded at30, 60, and 120 minutes after the injection process. According to the results, ICV injection of glutamate considerably reduced food intake (p<0.05). Co-injection of α-FMH + glutamate and/or chlorpheniramine + glutamate reduced the hypophagic influence of glutamate (p<0.05), whereas thioperamide + glutamate augmented glutamate-induced hypophagia in neonatal chicks (p<0.05). Co-injection of MK-801 + histamine or UBP-302 + histamine reduced the hypophagic influence of the histamine (p<0.05), whereas LY341495 + histamine augmented the hypophagic influence of the histamine (p<0.05). Given the results, it is suggested that the effect of the connection between these systems on the process of food intake regulation is mediated by H₁ and H₃ histamines as well as NMDA, Kainate, and mGluR₂ glutamate receptors in neonatal layer chickens.