Central dopaminergic, serotoninergic, as well as GABAergic systems mediate NMU-induced hypophagia in newborn chicken

Abstract

Aim

Dopaminergic, serotoninergic, and GABAergic systems influence feeding; however, it is unknown how these chemicals interact with neuromedin U (NMU)-induced feeding in birds. In the current study, ten trials were conducted to determine the links between the above-mentioned systems and NMU.

Materials and Methods

In the foremost experimentation, chickens were given intracerebroventricularly injections of NMU (0.1, 1, and 10 µg). NMU (10 µg), SCH23390 (5 nmol), a D₁ receptor antagonist, and NMU + SCH23390 were administered in the second experiment. In subsequent experiments, instead of SCH23390, were applied AMI-193 (5 nmol D₂ receptor antagonist), NGB2904 (6.4 nmol D₃ receptor antagonist), L-741,742 (6 nmol D₄ receptor antagonist), 6-OHDA (2.5 nmol dopamine inhibitor), SB242084 (5-HT_2c receptor antagonist, 1.5 μg), 8-OH-DPAT (5-HT_1A receptor agonist, 15.25 nmol), picrotoxin (GABA_A receptor antagonist, 0.5 μg), and CGP54626 (GABA_B receptor antagonist, 20 ng). Then, cumulative intake of food was recorded for 2 h.

Results

According to the results, NMU reduced feeding when compared to the control group (p < 0.05). The NMU-induced hypophagia was reduced with co-injection of NMU and SCH23390 (p < 0.05). Hypophagia was diminished with NMU and AMI-193 (p < 0.05). NMU + NGB2904 and NMU + L-741,742 co-injections had no influence (p > 0.05). 6-OHDA reduced the hypophagia (p < 0.05). NMU and SB242084 decreased the hypophagia (p < 0.05), whereas NMU and 8-OH-DPAT had no effect (p > 0.05). The effects were amplified with picrotoxin (p < 0.05). NMU with CGP54626 had no influence on the hypophagia (p > 0.05).

Conclusion

Thus, NMU-induced hypophagia is probably mediated by D₁/D₂, 5-HT_2c, and GABA_A receptors in neonatal chicks.

Keywords:

• Neuromedin U
• dopaminergic system
• serotoninergic system
• GABAergic system
• food intake

Acknowledgments

The authors thank the central laboratory (Dr. Rastegar Lab.) of the Faculty of Veterinary Medicine, the University of Tehran, for cooperation. This research is conducted as a part of the Ph.D. thesis of the first author.

Statements & declarations

Author contributions

All authors have agreed to be named as authors of this manuscript. Any work (data, text, or theories) of others besides the authors have been properly acknowledged. The work is original and not previously published. All data are true and accurate to the knowledge of the authors.

Compliance with ethical standards

 

Informed consent

This manuscript does not contain any studies with human subjects performed by any authors.

Research involving human and/or animals rights

All experiments were executed according to the Guide for the Care and Use of Laboratory Animals and were approved by the institutional animal ethics committee.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.