PT  - JOURNAL ARTICLE
AU  - Shojaei, M.
AU  - Zendehdel, M.
AU  - Babapour, V.
AU  - Charkhkar, S.
AU  - Hassanpour, S.
TI  - Opioid-induced hypophagia is mediated by 5-HT<sub>2</sub>c receptors in neonatal layer-type chicken
DP  - 2015 Sep 30
TA  - Czech Journal of Animal Science
PG  - 400--410
VI  - 60
IP  - 9
AID - 10.17221/8458-CJAS
IS  - 12121819
AB  - Opioidergic and serotonergic (5-HTergic) systems have crucial role in central regulation of food intake. This study was designed to investigate the role of the opioidergic system and the interaction with the 5-HTergic system in opioid-induced feeding behaviour in 3-h food-deprived (FD<sub>3</sub>) neonatal layer-type chicks. In total 432 chickens were allocated into 9 experiments, each per 4 treatment groups. In Experiment 1, birds were intracerebroventricularly (ICV) injected with D-Ala2-NMe-Phe4-Glyol5-enkephalin (DAMGO), µ-opioid receptor agonist (125, 250, and 500 pmol). In Experiment 2, chickens were ICV treated with D-Pen<sup>2</sup>, D-Pen<sup>5</sup>enkephalin (D-Pen<sup>2,5</sup>enkephalin, DPDPE), δ-opioid receptor agonist (20, 40, and 80 pmol). In Experiment 3, the effect of ICV injection of U-50488H, κ-opioid receptor agonist (10, 20, and 30 nmol) was investigated in chicks. In Experiment 4, chickens were injected with para-chlorophenylalanine (PCPA), cerebral serotonin depletive (1.5 µg) + DAMGO (125 pmol). In Experiment 5, birds were treated with PCPA (1.5 µg) + DPDPE (40 pmol). In Experiment 6, birds received 1.5 µg PCPA + U-50488H (30 nmol). In Experiments 7-9, birds were injected like in Experiments 4-6, but with SB242084, 5-HT<sub>2</sub>c receptor antagonist (1.5 µg) instead of the PCPA injection. Cumulative food intake was recorded until 3 h post injection. According to the results, the ICV injection of DAMGO significantly decreased whereas that of DPDPE + U-50488H increased food intake (P ≤ 0.05). Co-administration of PCPA + DAMGO significantly decreased hypophagia induced by DAMGO (P ≤ 0.05). PCPA had no effect on DPDPE + U-50488H-induced hyperphagia (P ≥ 0.05). SB242084 significantly attenuated the hypophagic effect of DAMGO (P ≤ 0.05), while SB242084 had no modulatory effect on the food intake induced by DPDPE + U-50488H (P ≥ 0.05). These results suggest that there is an interaction between the opioidergic and 5-HTergic systems mediating the hypophagic effect of µ-opioid receptors via the 5-HT<sub>2</sub>c receptor in neonatal layer-type chicks.