μ-Opioid receptor agonist diminishes POMC gene expression and anorexia by central insulin in neonatal chicks

Shiraishi Jun-ichi

Yanagita Kouichi

Fujita Masanori

Bungo Takashi

Neuroscience Letters

Pro-opiomelanocortin (POMC) neurons in the hypothalamus are direct targets of peripheral satiety signals, such as leptin and insulin in mammals. The stimulation of these signals activates hypothalamic POMC neurons and elevates POMC-derived melanocortin peptides that inhibit food intake in mammals. On the other hand, it has been recognized that β-endorphin, a post-translational processing of POMC, acts in an autoreceptor manner to the μ-opioid receptor (MOR) on POMC neurons, diminishing POMC neuronal activity in mammals. Recently, we found that central insulin functions as an anorexic peptide in chicks. Thus, the present study was done to elucidate whether β-endorphin affects the activation of POMC neurons by insulin in neonatal chicks. Consequently, quantitative real-time PCR analysis shows that intracerebroventricular (ICV) injection of insulin with β-endorphin significantly decreases brain POMC mRNA expression when compared with insulin alone. In addition, co-injection of MOR agonist (β-endorphin or [d-Ala2, N-MePhe4, Gly5-ol]-enkephalin (DAMGO)) significantly attenuates insulin-induced hypophagia in chicks. These data suggest that β-endorphin regulates the activity of the central melanocortin system, and its activation may provide an inhibitory feedback mechanism in the brain of neonatal chicks.

β-Endorphin

food intake

insulin

central nervous system

neonatal chick

melanocortin system

Zoology [ 480 ]

eng

Elsevier Ireland Ltd

Copyright (c) 2008 Elsevier Ireland Ltd

[ISSN] 0304-3940

[NCID] AA00754925

[DOI] 10.1016/j.neulet.2008.05.040

[DOI] http://dx.doi.org/10.1016/j.neulet.2008.05.040 isVersionOf