Interaction between leptin and glutamatergic system on food intake regulation in neonatal chicken: role of NMDA and AMPA receptors.

The aim of the current study was to determine the possible interaction of the central leptin and Glutamatergic systems on feeding behavior in neonatal 3-hours food deprived (FD) broilers chickens. In experiment 1, FD chicken received intracerebroventricular (ICV) injection of control solution (group i) and 2.5, 5 and 10 µg of Leptin (groups ii-iv). In experiment 2, FD chicken were ICV injected with (group i) control solution and groups ii-iv with 2.5, 5 and 10 nmol of AG-490 (JAK antagonist). In experiment 3, injections were (i) control solution, (ii) Leptin (10 µg), (iii) AG-490 (2.5 nmol) and (iv) Leptin + AG-490. In experiment 4, broiler chickens were ICV injected with (i) control solution, (ii) Leptin (10 µg), (iii) MK-801 (NMDA glutamate receptors antagonist; 15 nmol) and (iv) Leptin + MK-801. Experiments 5-9 were similar to experiment 1, except chicken were ICV injected with CNQX (AMPA receptor antagonist, 390 nmol), UBP-302 (Kainate receptor antagonist, 390 nmol), AIDA (mGluR1 antagonist, 2 nmol), LY341495 (mGluR2 antagonist, 150 nmol) and UBP1112 (mGluR3 antagonist, 2 nmol) instead of MK-801. Then, food intake was measured until 120 min after injection. ICV injection of leptin (2.5, 5 and 10 µg) significantly decreased food intake in a dose dependent manner ( < 0.05). Also, ICV injection of the JAK antagonist (2.5, 5 and 10 nmol) had hyperphagic effect in chicken ( < 0.05). Co-administration of leptin + AG-490, partially decreased leptin-induced hypophagia in broiler chicken ( < 0.05). In addition, co-injection of leptin + MK-801 significalty inhibited leptin-induced hypophagia in neonatal chicken ( < 0.05). Also, co-administration of leptin + CNQX partially attenuated hypophagic effect of leptin in chicken ( < 0.05). The results of present study suggest that leptin has hypophagic effect in neonatal chicken and this effect is probably mediated NMDA and AMPA glutamatergic receptors.