MICROSCOPY Vol.46▶No.2 2011

Newly Bioactive Peptide “Kisspepitin” and Its Role for the Neuronal Regulation System for Reproduction ~New Aspect of Hypothalamus-Pituitary-Gonad (HPG) Axis~

Hitoshi Ozawa, Ken Takumi, Nobuhiko Sawai, Kinuyo Iwata, Ryo Nakane and Norio Iijima

Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School

Abstract: A newly reported bioactive peptide, kisspeptin and its receptor (Kiss1r or GPR54) have an important role as key player in the regulation of reproduction. Mutations of the peptide and its receptor cause profound hypothalamic hypogonadotropic hypogonadism. Kisspeptin neurons are expressed in the hypothalamus, as well as other brain region in many vertebrates. Kisspeptin neurons directly project to GnRH neurons and may stimulate to secrete GnRH. Kisspeptin neurons show sexually difference with respect to the number of neurons and transcription activity in certain nuclei in the brain, and some kisspeptin neurons coexpress other transmitters, dynorphin and neurokinin B. Kisspeptin signaling system mediated by estrogen via estrogen receptor a has been related in mediateing the positive and negative feedback action of sex steroids on LH/FSH secretion, generating the preovulatory GnRH and/or LH surge, and triggering and guiding the onset of puberty.
In this review, we introduce the morphological characteristics and many important physiological function of kisspeptin and its receptor.

Key words: Kisspepitin, Kisspeptin receptor (Kiss1r or GPR54), GnRH, Puberty, Reproductive regulation