Progress in Reproductive Neuroendocrinology in Vertebrates

It has been believed that gonadotropin-releasing hormone (GnRH) is the only hypothalamic neuropeptide that regulates the hypothalamic-pituitary-gonadal (HPG) axis in vertebrates since its discovery at the beginning of 1970s. However, two new key hypothalamic neuropeptides, i.e. gonadotropin-inhibitory hormone (GnIH) and kisspeptin, have been found to play key roles in the control of reproduction at the beginning of 2000s. In 2000, GnIH was discovered in the quail hypothalamus. Following intensive research showed that GnIH inhibits gonadotropin synthesis and release through actions on GnRH neurons and gonadotropes via GPR147 in birds and mammals. GnIH peptides were also identified in other vertebrate species from fish to humans. As in birds, mammalian and fish GnIH peptides inhibit gonadotropin release, indicating the conserved inhibitory role of GnIH in the regulation of the HPG axis in vertebrates. Following the discovery of GnIH, kisspeptin, encoded by the Kiss1 gene, was discovered in mammals. In contrast to GnIH, kisspeptin has a stimulatory effect on GnRH neurons via GPR54. The Kiss1 gene has also been identified in amphibians and fish. Thus, we now know that GnRH is not the sole hypothalamic neuropeptide controlling vertebrate reproduction.

The aim of this Flagship Research Topic, “Progress in Reproductive Neuroendocrinology in Vertebrates” is to review the discoveries of GnIH and kisspeptin and the progress in reproductive neuroendocrinology made by these new key hypothalamic neuropeptides by collecting review articles from leading scientists in this new research field.