Evidence that estrogen mediates the positive feedback effect on GnRH

Abstract

Kisspeptin (Metastin), a protein encoding by the KiSS-1 gene, is a ligand for the G protein-coupled receptor GPR54. To investigate the molecular consequences of estrogen secretion on brain, estradiol benzoate was intravenously injected to sheep, and the expression of kisspeptin and Fos-like protein were scanned in the neurons of arcuate nucleus (ARC) by immunohistochemistry. In the case of Fos, the results showed that the number of immunopositive-Fos cells in ARC was significantly greater in the estradiol benzoate-treated OVX ewes 1 h after the injection. Similarly, estrogen injection activated the expression of kisspeptin within 1 h of injection. The results suggest an acute effect of estrogen -through kisspeptin, initiating the events leading to the positive feedback effect on pulsatile secretion of gonadotrophin releasing hormone (GnRH).