Gonadotrophin Inhibitory Hormone Depresses Gonadotrophin α and Follicle-Stimulating Hormone β Subunit Expression in the Pituitary of the Domestic Chicken

Studies performed in vitro suggest that a novel 12 amino acid RF amide peptide, isolated from the quail hypothalamus, is a gonadotrophin inhibitory hormone (GnIH). The aim of the present study was to investigate this hypothesis in the domestic chicken. Injections of GnIH into nest‐deprived incubating hens failed to depress the concentration of plasma luteinizing hormone (LH). Addition of GnIH to short‐term (120 min) cultures of diced pituitary glands from adult cockerels depressed follicle‐stimulating hormone (FSH) and LH release and depressed common α and FSHβ gonadotrophin subunit mRNAs, with no effect on LHβ subunit mRNA. Hypothalamic GnIH mRNA was higher in incubating (out‐of‐lay) than in laying hens, but there was no significant difference in the amount of hypothalamic GnIH mRNA in out‐of‐lay and laying broiler breeder hens at the end of a laying year. It is concluded that avian GnIH may play a role in controlling gonadotrophin synthesis and associated constitutive release in the domestic chicken.