Interaction between central GABAA receptor and dopaminergic system on food intake in neonatal chicks: role of D 1 and GABA A receptors.

OBJECTIVE: The present study was designed to examine the role of central γ-Aminobutyric acidA receptors and dopaminergic system on feeding behaviour in neonatal layer-type chicken.

METHODS: In this study, six experiments were designed, each with four treatment groups (n = 44 in each experiment). In experiment 1, four groups of 3-h food-deprived chicks received a dose of either the intracerebroventricular injection of (1) control solution, (2) Levo-dihydroxyphenylalanine as precursor of dopamine; 125 nmol, (3) Gaboxadol (γ-Aminobutyric acidA receptor agonist, 0.2 µg) and (4) Levo-dihydroxyphenylalanine (125 nmol) plus Gaboxadol (0.2 µg). Experiments 2-6 were similar to experiment 1, except that the chickens were intracerebroventricular-injected with 6-hydroxydopamine (is a neurotoxin; 2.5 nmol), SCH23390 (D1 receptor antagonist, 5 nmol), AMI-193 (D2 receptor antagonist, 5 nmol), NGB2904 (D3 receptor antagonist, 6.4 nmol) and L-741,742 (D4 receptor antagonist, 6 nmol) instead of levo-dihydroxyphenylalanine. Then, the cumulative food intake was measured until 120 min post-injection.

RESULTS: According to the results, intracerebroventricular injection of Gaboxadol (0.2 µg) significantly increased the food intake (P < 0.05). Co-injection of the 6-hydroxydopamine + Gaboxadol significantly amplified the food intake (P < 0.05). Intracerebroventricular injection of SCH23390 (5 nmol) + Gaboxadol (0.2 µg) significantly amplified the Gaboxadol-induced hyperphagia (P < 0.05). No significant effect was observed by co-injection of the D2 -D4 receptor antagonists + Gaboxadol (P > 0.05).

CONCLUSION: These results suggested the interconnection between central Dopaminergic and γ-Aminobutyric acidA on the feeding behaviour mediates via D1 and γ-Aminobutyric acidA receptors in 3-h food-deprived neonatal layer-type chicken.