Effects of gonadotropin-inhibitory hormone on folliculogenesis and steroidogenesis of cyclic mice

Objective: To evaluate the effects of gonadotropin-inhibitory hormone (GnIH) treatment on ovarian activity of mice. Design: Animal study. Setting: Reproductive physiology laboratory of university department of zoology. Animal(s): Twelve-week-old female mice of inbred Parkes strain. Intervention(s): Mice treated with different doses of GnIH (control, 100 ng, 500 ng, and 2 μg per day) for 8 days were studied. For in vitro study, the ovaries of proestrus mice were cultured with different doses of GnIH for 24 hours at 37°C. Main Outcome Measure(s): Folliculogenesis, steroidogenesis, luteogenesis, and apoptosis in the ovaries of control and GnIH-treated mice. Result(s): GnIH treatment produced significant changes in body mass, circulating steroid levels, and ovarian activity in the mice. GnIH also caused dose-dependent histologic changes in follicular development and luteinization. The antral follicles showed abnormal changes. The mice treated with increasing dose of GnIH showed significant changes in steroid synthesis owing to inhibitory effects of GnIH on ovarian expression of LH receptor, steroidogenic acute regulatory, and 3β-hydroxysteroid dehydrogenase proteins. Conclusion(s): GnIH inhibited follicular development and steroidogenesis in the ovary of mice. This study thus suggests biologic significance of this neuropeptide in regulating ovarian activity.