Reproduction in vertebrates is a complex process regulated by many hormones, and by paracrine factors and their receptors. This study aimed to examine the expression of pjGonadotropin-releasing hormone (GnRH 1), the kisspeptin receptor 2 (kissr2), and estradiol receptors α and β (ER α and ER β) during different stages of the sexual cycle and their distribution within the anterior brain of females of Chirostoma humboldtianum. Among these molecules, the kissr2 showed the maximal variation in expression, while GnRH 1 showed minimal variation of expression, and ERβ and ERα had intermediate variation of expression. The distribution of these molecules in the anterior brain was consistent with their levels of expression; kissr2 was widely distributed throughout the telencephalon and diencephalon, while ER and GnRH 1 showed more restricted distributions. No coexpression of kissr2 and ER in GnRH 1ergic neurons, suggesting that regulation of this GnRH variant is indirectly mediated by kisspeptin and estradiol.

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