Kisspeptins
encoded by Kiss1 gene
play pivotal roles in the regulation of reproduction. Recently
several studies reported a sex difference in Kiss1 expression in the arcuate nucleus (ARC) during the neonatal period. In this study
we investigated the effect of gonadal steroid manipulation on the sex difference in Kiss1 expression in ARC of rats. At neonatal and prepubertal stages
females had a greater number of Kiss1 neurons than the males. Gonadectomy at those stages resulted in significant increases in the Kiss1 neuron number and the sex differences disappeared. We also confirmed the expression of estrogen receptor alpha in kisspeptin neurons in neonates. Altogether
our results indicate that ARC Kiss1 expression is negatively regulated by gonadal steroids from early postnatal stages
and that the sex difference in ARC Kiss1 expression is attributed to the difference in circulating gonadal steroid levels. We also found that neonatal estrogenization inhibits Kiss1 expression and impairs negative feedback system.
