Ki: 1.03±0.41 nM (GPR10, human PrRP 1-31), 0.33±0.11 nM (GPR10, rat PrRP 1-31)

Prolactin Releasing Peptide (PrRP) has been identified as a specific, high affinity endogenous ligand for GPR10. Prolactin Releasing Peptide (PrRP) preproprotein can be cleaved at two different positions to give rise to two forms of 31 or 20 amino acids; Prolactin Releasing Peptide (PrRP)-31 and Prolactin Releasing Peptide (PrRP)-20 respectively. Rat Prolactin Releasing Peptide (PrRP) has also been identified and occurs as 31 or 20 amino acid forms; these peptides are highly conserved between species. Human PrRP-20, human PrRP-31, rat PrRP-20 and rat PrRP-31 display high affinity for GPR10 receptors, with K _i values of 0.26±0.07, 1.03±0.41, 0.22±0.06 and 0.33±0.11 nM, respectively.

Following intracerebroventricular injection of Prolactin Releasing Peptide (1-31), human 5 nM there is a highly significant simulation of plasma LH that began at 10 minutes and is maintained over the course of the experiment. Plasma FSH increased at 20 minutes following ICV injection. Total plasma testosterone increased at 60 minutes post injection.