Kisspeptin (also known as metastin), a hypothalamic peptide, has attracted 
attention as a key molecule in the release of gonadotrophin-releasing hormone 
(GnRH) in various mammalian species, such as rodents, sheep and primates. Two 
populations of kisspeptin neurones in the brain may control two modes of GnRH 
release to time the onset of puberty and regulate oestrous cyclicity in rats and 
mice. One population of kisspeptin neurones, located in the anteroventral 
periventricular nucleus, appears to be responsible for the induction of the GnRH 
surge that leads to the luteinising hormone surge and ovulation. The other, 
located in the hypothalamic arcuate nucleus, appears to be involved in 
generating GnRH pulses, resulting in luteinising hormone pulses followed by 
follicular development and steroidogenesis in the ovary. The present review 
focuses on the physiological role of the two populations of kisspeptin neurones 
in controlling gonadal functions by generating the two modes of GnRH release in 
a female rat model.