Estrogen upregulates the firing activity of hypothalamic gonadotropin‐releasing hormone (GnRH1) neurons in the evening in female medaka

Abstract

The reproductive function of vertebrates is regulated by the hypothalamic-pituitarygonadal axis. In sexually mature females, gonadotropin-releasing hormone (GnRH) neurons in the preoptic area (POA) are assumed to be responsible for a cyclic large increase in GnRH release, the GnRH surge, triggering a luteinizing hormone (LH) surge, which leads to ovulation. Precise temporal regulation of the preovulatory GnRH/ LH surge is important for successful reproduction because ovulation should occur after follicular development. The time course of the circulating level of estrogen is How to cite this article: Ikegami K, Kajihara S, Umatani C, Nakajo M, Kanda S, Oka Y. Estrogen upregulates the firing activity of hypothalamic gonadotropin-releasing hormone (GnRH1) neurons in the evening in female medaka.

AgRP1 modulates breeding season-dependent feeding behavior in female medaka

“…shows high blood concentration of E2 (Ikegami et al, 2022), this pathway may be important for breeding season-dependent feeding behavior. Especially, in teleost, main egg protein for nutrition is vitellogenin, whose expression is also facilitated by E2 (Tohyama et al, 2017).…”

“…Among various factors associated with sexual maturity, estrogens are known to be abundantly released from mature ovary and play important roles in reproductive readiness, sexual behavior, and so on (Jennings & de Lecea, 2020;Naftolin et al, 2007;Adachi et al, 2007;Clarkson & Herbison, 2009;Wintermantel et al, 2006;Micevych & Meisel, 2017;Melo & Ramsdell, 2001). Among the ovarian estrogens, 17β-estradiol (E2) is the major factor important for reproduction (Kanda et al, 2011;Kelly & Qiu, 2010), and the blood E2 concentration of LD-conditioned female medaka is higher than those of SD (Ikegami et al, 2022). Thus, we hypothesized that E2 regulates the expression of agrp1 and npyb under the condition of breeding season.…”