Glycyl-l-glutamine attenuates NPY-induced hyperphagia via the melanocortin system.

This study aimed to determine whether glycyl-l-glutamine (Gly-Gln; ß-endorphin (30-31)), a non-opioid peptide derived from ß-endorphin processing, modulates neuropeptide Y (NPY)-induced feeding and hypothalamic mRNA expression of peptide hormones in male broiler chicks. Intracerebroventricular injection of NPY (235 pmol) generated a hyperphagic response in ad libitum chicks within 30 min. Co-administration of Gly-Gln (100 nmol) attenuated this response, inducing a 30 % decrease. This was not attributable to Gly-Gln hydrolysis because co-administration of glycine (Gly) and glutamine (Gln) had no effect on NPY-induced hyperphagia. Gly-Gln injected alone also showed no effect. The hypothalamic pro-opiomelanocortin mRNA expression in the co-injection group was significantly higher than that in the NPY alone group. These data indicate that endogenous Gly-Gln may contribute to regulate feeding behavior via the central melanocortin system in chicks and acts as a counter regulator of the neural activity in energy metabolism.

Effect of Stereotaxic Surgery of the Third Ventricle on Growth Performance in Neonatal Chicks.

Feeding behavior and energy metabolism are precisely regulated by humoral and/or neural factors in the central nervous system. In particular, nuclei, such as the arcuate nucleus, ventromedial hypothalamic nucleus, and lateral hypothalamic area located near the third ventricle of the hypothalamus are the centers of feeding and energy metabolism in various vertebrate species, including chickens. In this study, we evaluated the effects of cannulation of the third ventricle on chick growth and feeding behavior in the neonatal stage, to develop a method for local and chronic central nervous system-mediated energy metabolism. Referring to the chick brain atlas, a guide cannula was inserted into the third ventricle of the chick under anesthesia immediately after hatching using a stereotaxic instrument. The chicks that recovered from anesthesia were bred for 11 days under normal feeding management conditions, and then feed intake amount, body weight gain, and metabolic tissue weight were measured. The effects of direct stimulation of the third ventricle with 2-deoxy-D-glucose on the expression level of the immediate-early gene, cFOS, and feed intake in 5-day-old chicks were also evaluated. There were no differences in feed intake, body weight gain, and metabolic tissue weight between 11-day-old cannulated and control chicks. The expression of cFOS mRNA in the ventromedial hypothalamic nucleus was higher than that in the amygdala after the third ventricular administration of 2-deoxy-D-glucose. Additionally, direct third ventricular injection of 2-deoxy-D-glucose attenuated the feeding behavior of chicks for a while. Overall, we speculate that the technique is effective for local and/or chronic stimulation of the nucleus near the third ventricle of the chick hypothalamus, which is important for feed and energy metabolism regulation.

A genetically female brain is required for a regular reproductive cycle in chicken brain chimeras.

Sexual differentiation leads to structural and behavioural differences between males and females. Here we investigate the intrinsic sex identity of the brain by constructing chicken chimeras in which the brain primordium is switched between male and female identities before gonadal development. We find that the female chimeras with male brains display delayed sexual maturation and irregular oviposition cycles, although their behaviour, plasma concentrations of sex steroids and luteinizing hormone levels are normal. The male chimeras with female brains show phenotypes similar to typical cocks. In the perinatal period, oestrogen concentrations in the genetically male brain are higher than those in the genetically female brain. Our study demonstrates that male brain cells retain male sex identity and do not differentiate into female cells to drive the normal oestrous cycle, even when situated in the female hormonal milieu. This is clear evidence for a sex-specific feature that develops independent of gonadal steroids.