Prokineticin-2 and function
The signals generated by the HPG axis, the main participants of which are gonadotropin-releasing hormone (GnRH), gonadotropins, and sex steroids, coordinate the development and functioning of the immune system, and immunomediators, in particular, cytokines and thymic peptides, influence the HPG axis.
The mechanism of GnRH secretion regulation in the hypothalamus includes a network of various neurons, including KISS1-producing ones, which can act on GnRH neurons through separate or multiple neuronal systems . GnRH- and KISS1 neurons are located in the same regions of the hypothalamus, and GnRH neurons express KISS1R. Axons of KISS1 neurons form pericapillary plexuses at the site of GnRH secretion . Neurokinin B (NKB) and dynorphin, which colocalize with KISS1 in the arcuate nucleus and are linked by axosomatic synapses, are also involved in the generation of GnRH impulses . It is assumed that NKB initiates the onset of GnRH impulse secretion, while dynorphin initiates its termination . General cues of GnRH neuron regulation in HPG axis is presented on Figure 1.