title: Green light inhibits GnRH-I expression by stimulating the melatonin-GnIH pathway in the chick brain.
abstract: To study the mechanism by which monochromatic light affects gonadotrophin-releasing hormone (GnRH) expression in chicken hypothalamus, a total of 192 newly-hatched chicks were divided into intact, sham-operated and pinealectomy groups and exposed to white (WL), red (RL), green (GL) and blue (BL) lights using a light-emitting diode system for 2 weeks. In the GL intact group, the mRNA and protein levels of GnRH-I in the hypothalamus, the mean cell area and mean cell optical density (OD) of GnRH-I-immunoreactive (-ir) cells of the nucleus commissurae pallii were decreased by 13.2%-34.5%, 5.7%-39.1% and 9.9%-17.3% compared to those in the chicks exposed to the WL, RL and BL, respectively. GL decreased these factors related to GnRH-I expression and the effect of GL was not observed in pinealectomised birds. However, the mRNA and protein levels of hypothalamic gonadotrophin-inhibitory hormone (GnIH) and GnIH receptor (GnIHR), the mean cell area and mean cell OD of the GnIH-ir cells of the paraventricularis magnocellularis, and the plasma melatonin concentration in the chicks exposed to GL were increased by 18.6%-49.2%, 21.1%-60.0% and 8.6%-30.6% compared to the WL, RL and BL intact groups, respectively. The plasma melatonin concentration showed a negative correlation with GnRH-I protein and a positive correlation with GnIH and GnIHR proteins. Protein expression of both GnRH-I and GnIHR showed a negative correlation in the hypothalamus. After pinealectomy, GnRH-I expression increased, whereas plasma melatonin concentration, GnIH and GnIHR expression decreased, and there were no significant differences among the WL, RL, GL and BL groups. Double-labelled immunofluorescence showed that GnIH axon terminals were near GnRH-I neurones, some GnRH-I neurones coexpressed with GnIHR and GnIH neurones coexpressed with melatonin receptor subtype quinone reductase 2. These results demonstrate that green light inhibits GnRH-I expression by increasing melatonin secretion and stimulating melatonin receptor-GnIH-GnIH receptor pathway in the chick brain.
authors.affiliation: Laboratory of Anatomy of Domestic Animal, College of Animal Medicine, China Agricultural University, Beijing, China.
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Changping Hospital of Integrated Chinese and Western Medicine, Beijing, China.
authors.forename: F
authors.initials: F
authors.lastname: Chen
authors.affiliation: Laboratory of Anatomy of Domestic Animal, College of Animal Medicine, China Agricultural University, Beijing, China.
authors.forename: J
authors.initials: J
authors.lastname: Cao
authors.affiliation: Laboratory of Anatomy of Domestic Animal, College of Animal Medicine, China Agricultural University, Beijing, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Dong
authors.affiliation: Laboratory of Anatomy of Domestic Animal, College of Animal Medicine, China Agricultural University, Beijing, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.affiliation: College of Animal Medicine, Agricultural University of Hebei, Baoding, China.
authors.forename: M
authors.initials: M
authors.lastname: Hu
authors.affiliation: Laboratory of Anatomy of Domestic Animal, College of Animal Medicine, China Agricultural University, Beijing, China.
authors.forename: Y
authors.identifier: 0000-0003-2576-5977
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000378:metabolism*; D002645:Chickens; D007028:Hypothalamic Hormones / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism*; D008027:Light; D008297:Male; D008550:Melatonin / Q000097:blood / Q000378:metabolism*; D009412:Nerve Fibers / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D030161:Avian Proteins; D007028:Hypothalamic Hormones; D008550:Melatonin
keywords: GnIH; GnRH-I; chicken; hypothalamus; melatonin; monochromatic light