Effect of Neurokinin B on expression of GnRH and kisspeptin in the hypothalamus of rat

Abstract： The aim of study is to investigate the effect of central administration of neurokinin B (NKB) on the timing of puberty onset and the expression levels of kisspeptin and gonadotrophin releasing hormone (GnRH) genes and proteins in the hypothalamus of rats. Prepubertal Sprague-Dawley rats were divided into three groups: NKB, vehicle, and control groups. The rats in the NKB group received intracerebroventricular injection of NKB solution, those in the vehicle group received injections of an equal volume of saline, and those in the control group did not receive any treatment. The rats were sacrificed, and the hypothalamus was obtained, sectioned, and used for fluorescence immunocolocalization of GnRH and kisspeptin immunoreactivity. Total RNA was extracted and quantified, and the DNA was analyzed using RT-PCR. The results of this study demonstrated that NKB treatment of prepubertal rats expedited the timing of vaginal opening (VO) and increased the ovary and uterus weights. Additionally, the hypothalamic expression of Kiss1 and GnRH mRNA and the number of GnRH-immunoreactive (ir) cells number significantly decreased (P < 0.05) in the arcuate nucleus (ARC) but increased in the paraventricularis nucleus (PVN) and median eminence (ME), while the number of kisspeptin-ir cells significantly increased (P < 0.05) in the ARC and periventricular nucleus (PeN) relative to the control. There were no differences (P > 0.05) in the number of kisspeptin-ir cells in the PVN. Overall, the results suggest that NKB plays a major role in modulating the activity of kisspeptin and GnRH during puberty. Nevertheless, both kisspeptin and GnRH serve different functions in the in the different nuclei of the hypothalamus during the onset of puberty.