The Role of GnIH in Biological Rhythms and Social Behaviors.

Gonadotropin-inhibitory hormone (GnIH) was first discovered in the Japanese quail, and peptides with a C-terminal LPXRFamide sequence, the signature protein structure defining GnIH orthologs, are well conserved across vertebrate species, including fish, reptiles, amphibians, avians, and mammals. In the mammalian brain, three RFamide-related proteins (RFRP-1, RFRP-2, RFRP-3 = GnIH) have been identified as orthologs to the avian GnIH. GnIH is found primarily in the hypothalamus of all vertebrate species, while its receptors are distributed throughout the brain including the hypothalamus and the pituitary. The primary role of GnIH as an inhibitor of gonadotropin-releasing hormone (GnRH) and pituitary gonadotropin release is well conserved in mammalian and non-mammalian species. Circadian rhythmicity of GnIH, regulated by light and seasons, can influence reproductive activity, mating behavior, aggressive behavior, and feeding behavior. There is a potential link between circadian rhythms of GnIH, anxiety-like behavior, sleep, stress, and infertility. Therefore, in this review, we highlight the functions of GnIH in biological rhythms, social behaviors, and reproductive and non-reproductive activities across a variety of mammalian and non-mammalian vertebrate species.

Effects of nonylphenol administration on serum, liver and testis estrogen metabolism.

PURPOSE: Nonylphenol (NP) is one widely distributed representative of environmental estrogens that disturb reproductive activities, bone metabolism and brain function through interfering diverse signal pathways leading to hormone metabolic dysfunctions, immunologic derangement, and tumorigenesis. Few of previous studies have observed the subacute toxicity on rodents, and little has been focused on the mechanism underneath the toxicities observed. METHODS: The 32 male Sprague-Dawley (SD) rats were randomly divided into four groups, the negative control group (corn oil) NP low, medium and high dose groups [30, 90, 270 mg/(kg·d)]. SD rats administrated with different dosage of NP every other day for 28d. Elisa and RT-PCR was employed to observe estrogen metabolism markers or mRNA expressions. RESULTS: In serum, NP exposure caused testosterone (T) (p < 0.001), progesterone (PROG) (p < 0.05) and estrone (E1) (p < 0.05) increased. In testicle, NP exposure caused T (p < 0.001), PROG (p < 0.05), E1 (p < 0.05), 17ß-estradiol (E2) (p < 0.05) and ERα mRNA (p < 0.01) increased, while P450 aromatizing enzyme (p < 0.001) decreased in NPL and ERß mRNA (p < 0.001) decreased in NPM and NPH. In liver, NP exposure caused 17ß-HSD2 mRNA (p < 0.01) increased, while P450 aromatizing enzyme decreased (p < 0.05). CONCLUSION: NP exposure exhibited general and estrogenic toxicity in rats through disturbing estrogen secretion network and estrogen receptor expression network, inducing abnormal metabolism of estrogen, whether in serum, liver and testicle.

Reproductiveaxis gene regulation during photostimulation and photorefractoriness in Yangzhou goose ganders.

BACKGROUND: The Yangzhou goose is a long-day breeding bird that has been increasingly produced in China. Artificial lighting programs are used for controlling its reproductive activities. This study investigated the regulations of photostimulation and photorefractoriness that govern the onset and cessation of the breeding period. RESULTS: Increasing the daily photoperiod from 8 to 12 h rapidly stimulated testis development and increased plasma testosterone concentrations, with peak levels being reached 2 months after the photoperiod increase. Subsequently, testicular activities, testicular weight, spermatogenesis, and plasma testosterone concentrations declined steadily and reached to the nadir at 5 months after the 12-hour photoperiod. Throughout the experiment, plasma concentrations of triiodothyronine and thyroxine changed in reciprocal fashions to that of testosterone. The stimulation of reproductive activities caused by the increasing photoperiod was associated with increases in gonadotropin-releasing hormone (GnRH), but decreases in gonadotropin-inhibitory hormone (GnIH) and vasoactive intestinal peptide (VIP) gene messenger RNA (mRNA) levels in the hypothalamus. In the pituitary gland, the levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) mRNA abruptly increased during the longer 12-hour photoperiod. The occurrence of photorefractoriness was associated with increased GnIH gene transcription by over 250-fold, together with increased VIP mRNA levels in the hypothalamus, and then prolactin and thyroid-stimulating hormone in the pituitary gland. FSH receptor, LH receptor, and StAR mRNA levels in the testis changed in ways paralleling those of testicular weight and testosterone concentrations. CONCLUSIONS: The seasonal reproductive activities in Yangzhou geese were directly stimulated by a long photoperiod via upregulation of GnRH gene transcription, downregulation of GnIH, VIP gene transcription, and stimulation of gonadotrophin. Development of photorefractoriness was characterized by hyper-regulation of GnIH gene transcription in the hypothalamus, in addition of upregulation of VIP and TRH gene transcription, and that of their receptors, in the pituitary gland.