Opioid-induced hypophagia is mediated by 5-HT2c receptors in neonatal layer-type chicken

M. Shojaei, M. Zendehdel, V. Babapour, S. Charkhkar and S. Hassanpour
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M. Shojaei: Section of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran
M. Zendehdel: Department of Physiology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
V. Babapour: Department of Physiology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
S. Charkhkar: Section of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran
S. Hassanpour: Section of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran

Czech Journal of Animal Science, 2015, vol. 60, issue 9, 400-410

Abstract: 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 (FD3) 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-Pen2, D-Pen5enkephalin (D-Pen2,5enkephalin, 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-HT2c 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-HT2c receptor in neonatal layer-type chicks.

Keywords: opioidergic; 5-HTergic system; food intake; layer-type chicks (search for similar items in EconPapers)
Date: 2015
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Persistent link: https://EconPapers.repec.org/RePEc:caa:jnlcjs:v:60:y:2015:i:9:id:8458-cjas

DOI: 10.17221/8458-CJAS

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