Age-dependent Kisspeptin Effects on the GnRH Neurons in Male and Female Mice

Abstract

Background: The gonadotropin releasing hormone (GnRH) neurons play a pivotal role in the central regulation of fertility. Kisspeptin binds to the G-protein coupled receptor 54 (GPR54) and GPR54 has been shown to be essential for puberty and subsequent fertility in humans. The recent in vivo studies have proved that kisspeptin is an extremely potent activator of GnRH neurons. However, the precise mechanism of action of kisspeptin on the GnRH neurons and the age-dependent kisspeptin effects are not yet fully understood. In this study, we investigated the effects of kisspeptin on the GnRH neurons over the developmental stages in male and female mice. Methods: Young ( P35) GnRH-GFP transgenic mice expressing green fluorescent protein were used in this study. Acute coronal brain slices containing the preoptic area were prepared, and the identified GnRH neurons were recorded using the gramicidin perforated-patch clamp technique. Results: In young mice, GnRH neurons were excited by bath application of kisspeptin in 36% (13/36) in male, 17% (4/23) in female tested neurons. In adult mice, GnRH neurons were excited in the majority (30/40, 75%) in male, (21/31, 68%) in female neurons tested. However, there was no significant difference between the effects of kisspeptin in male and female mice. In addition, we tested kisspeptin effects in diestrus, proestrus and estrus animals. There were no significant differences of kisspeptin effects over the estrous cycle. Kisspeptin failed to induce excitatory effects on GnRH neurons (6/7, 86%) neurons) by pretreatment of U73122, a protein lipase C (PLC) inhibitor and kisspeptin-induced excitatory effects were decreased by U73122 application (n = 2). Conclusion: These results demonstrated that kisspeptin-induced membrane excitability was increased after puberty and this supports a previous suggestion that GPR54 is essential for puberty and subsequent fertility. (J Korean Endocr Soc 23:302~309, 2008)