Fig. (1).

Schematic diagram of gastrin-releasing peptide (GRP)/GRP receptor (GRPR) systems, which control male sexual functions and itch transmission at the spinal cord level. This spinal center mediates penile reflexes and triggers ejaculation through androgen receptor (AR)-mediated mechanisms expressed in spinal GRP neurons. The somatosensory GRP system is located in the primary afferents, and the central axons of the primary afferents project to the spinal dorsal horn where GRPR is expressed at all spinal levels. (SNB, spinal nucleus of the bulbocavernosus; SPN, sacral parasympathetic nucleus).