摘要Objective: The present study is designed to investigate the cellular expressions and immunolocalizations of three different nitric oxide synthase(NOS)isoforms and the related nitric oxide(NO)/cyclic guanosine monophosphate(cGMP)signaling pathway in the ovaries of neonatal and immature rats.Methods: The ovaries were obtained from ICR(Institute for Cancer Research)female Sprague-Dawley rats at postnatal days 1,5,7,10,and 19.Then we carried out the histologic examination,immunohistochemistry,measurement of NOS activity,and modifications within the NO/cGMP pathway.Results: During postnatal days 1,5,7,10,and 19,all three isoforms of NOS were mainly localized to the oocytes and expressed as a gradual increase in granulosa cells and theca cells within the growing follicle.The ovarian total NOS activities and NO levels were increased at postnatal days 7 and 10 compared with other days.Conclusions: Our findings suggest that the locally produced NO and the NO/NOS signaling systems are involved in the follicular development to puberty.