The Role of GnIH in Paracrine/Autocrine Control of Ovarian Function in Zebrafish (Danio rerio)

Abstract

Gonadotropin inhibitory hormone (GnIH) is a hypothalamic neuropeptide, termed for its observed inhibitory effect on the luteinizing hormone release from cultured pituitary of Japanese quail when it was first discovered in 2000. In vertebrates including fish, GnIH has been found in extra-hypothalamic tissues including gonads, however, information regarding the role of this peptide as extra-pituitary regulator of gonadal function is not available and require further research. The goal of my thesis was to investigate direct action of GnIH, in vitro, on ovarian steroidogenesis, final oocyte maturation, and gene expression using sexually mature zebrafish. In the present study, GnIH did not significantly affect transcript levels for genes involved in the control of gonadal function and steroid biosynthesis. However, GnIH significantly altered hCG-induced estradiol (E2) release and resumption of meiosis. Thus, the findings provide a support for the hypothesis that GnIH plays paracrine/autocrine role in the regulation of ovarian function in zebrafish.