Cross-talk between gonadal gonadotropin-inhibitory hormone (GnIH) and thyroid hormones (THs) in the hypothalamic-pituitary-peripheral axis of zebrafish (Danio rerio)

Abstract

Thyroid hormones (T4/T3) exert several roles on regulating vertebrate homeostasis acting on several physiological processes such as growth, behavior, stress and on the reproductive system. In mammals, the role of thyroid hormones in reproduction has been well investigated, however the interaction between reproduction and thyroid axes is still unknown. This study aims to evaluate the role of thyroid hormones on zebrafish reproduction. To answer this question, a thyroid hormone disruptor, methimazole, will be used to generate a model of thyroid-induced insufficiency. Fish will be exposed to 1 mM of methimazole dissolved into the water for 21 days, after exposure they will be dissected and their testes will be collected for gene expression analyses of important elements of the HPG axis, such as GnRH and GnIH. Testes will then be submitted to an ex vivo organ culture system, in order to study the effects of GnIH and THs on spermatogenesis. We expect to clarify the mechanisms of cross-talk between GnIH and THs in the hypothalamic-pituitary-peripheral axis.