The Effects of Kisspeptin on Gonadotropin Release in Non-human Mammals

The Kiss1 gene encodes a 145-amino acid pre-peptide, kisspeptin, which is cleaved into smaller peptides of 54, 14, 13, and 10 amino acids. This chapter reviews in detail the effects of kisspeptin on gonadotropin secretion in non-human mammals. Studies of kisspeptin's effects have included both acute and chronic administration regimens via a number of administration routes. Acute kisspeptin stimulates gonadotropin secretion in a wide range of species of non-human mammals, including rats, mice, hamsters, sheep, pigs, goats, cows, horses, and monkeys. In general, the stimulatory effect of kisspeptin treatment is more pronounced for LH than FSH secretion. Kisspeptin is thought to exert its stimulatory effects on LH and FSH release via stimulation of GnRH release from the hypothalamus, since pre-administration of a GnRH antagonist prevents kisspeptin's stimulation of gonadotropin secretion. Although the kisspeptin receptor is also expressed on anterior pituitary cells of some species, and incubation of anterior pituitary cells with high concentrations of kisspeptin can stimulate in vitro LH release, the contribution of direct effects of kisspeptin on the pituitary is thought to be negligible in vivo. Continuous kisspeptin administration results in reduced sensitivity to the effects of kisspeptin, in some species. This desensitization is thought to occur at the level of the kisspeptin receptor, since the response of the pituitary gland to exogenous GnRH is maintained. Overall, the findings discussed in this chapter are invaluable to the understanding of the reproductive role of kisspeptin and the potential therapeutic uses of kisspeptin for the treatment of fertility disorders.