Roles of intracerebral activin, inhibin, and follistatin in the regulation of Kiss-1 gene expression: Studies using primary cultures of fetal rat neuronal cells.

Hypothalamic kisspeptin, encoded by the Kiss-1 gene, governs the hypothalamic-pituitary-gonadal axis by directly regulating the release of gonadotropin-releasing hormone. In this study, we examined the roles of activin, inhibin, and follistatin in the regulation of Kiss-1 gene expression using primary cultures of fetal rat neuronal cells, which express the Kiss-1 gene and kisspeptin. Stimulation with activin significantly increased Kiss-1 gene expression in these cultures by 2.02 ± 0.39-fold. In contrast, a significant decrease in Kiss-1 gene expression was observed with inhibin A and follistatin treatment. Inhibin B did not modulate Kiss-1 gene expression. Activin, inhibin, and follistatin were also expressed in fetal rat brain cultures and their expression was controlled by estradiol (E2). The inhibin α, ßA, and ßB subunits were upregulated by E2. Similarly, follistatin gene expression was significantly increased by E2 in these cells. Our results suggest the possibility that activin, inhibin, and follistatin expressed in the brain participate in the E2-induced feedback control of the hypothalamic-pituitary-gonadal axis.