Intracerebroventricular Injection of NMDA Receptor Antagonist Affects l-Arginine Induced Food Intake in Neonatal Layer Chicks

Abstract

Nowadays inquiry of possible interplay between different neurotransmitters in brain function is one of the major fields of interest for researchers. In the current study, we aimed to survey interaction between glutamatergic and nitrergic systems on food intake in layers. In this regards, total of 308 one-day-old female layer-type chicks divided to 28 groups of 11 individuals in 7 defined experiments. All chickens were kept 3 h food deprived and used for intracerebroventricular (ICV) injection in the 5 day olds. In experiments 1–5, treatment groups received ICV injection of 10 µl control solution, l-arginine (precursor of NO synthesis; 800 nmol). In addition, birds administrated by different antagonists of glutamatergic receptors including MK-801 (NMDA receptor antagonist; 15 nmol), CNQX (AMPA/kainate receptor antagonist; 390 nmol), AIDA (mGLUR1 glutamate receptor antagonist; 2 nmol), LY341495 (mGLUR2 glutamate receptor antagonist; 150 nmol), UBP1112 (mGLUR3 glutamate receptor antagonist; 2 nmol) besides combination of mentioned antagonists of glutamatergic receptors + l-arginine (800 nmol). In the experiment 6, groups injected by control solution, glutamate (300 nmol), l-NAME (100 nmol) besides combination of both drugs. In the experiment 7, birds were ICV injected by control solution, glutamate (75 nmol), l-arginine (200 nmol) and combination of glutamate + l-arginine. Then cumulative food intake measured as following a known amount of a diet was given to the animals after 30, 60 and 120 min post injection. Based on the results, administration of MK-801 (15 nmol) significantly attenuated hypophagic effect induced by l-arginine (800 nmol) in neonatal chicks (P 0.05). Furthermore, co-administration of sub-effective doses of glutamate with l-arginine made significant hypophagic effect in comparison with control group and any of treatment group, which received sole glutamate or only l-arginine (P < 0.05). As a conclusion, it seems central glutamatergic system is modulating hypophagic effect induced by nitrergic system through NMDA receptor in neonatal layer chicks. Apparently, l-arginine and glutamate neurotransmitters showed synergistic effect on regulating food intake in layers.