Abstract
RFamide-related peptide-3 (RFRP-3) is a recently discovered neuropeptide that has been proposed to play a role in the stress response. We aimed to elucidate the role of RFRP-3 and its receptor, NPFF1R, in modulation of stress and anxiety responses. To achieve this, we developed a new NPFF1R antagonist, since our results showed that the only commercially available putative antagonist, RF9 is in fact an agonist at both NPFF1R and the kisspeptin receptor, KISS1R. We report here the identification and pharmacological characterization of GJ14, a true NPFFR antagonist. In in vivo tests of hypothalamic-pituitary-adrenal (HPA) axis function, GJ14 completely blocked RFRP-3-induced corticosterone release and neuronal activation in corticotropin-releasing hormone (CRH) neurons. Furthermore, chronic infusion of GJ14 led to anxiolytic-like behavior while RFRP-3 infusion had anxiogenic effects. Mice receiving chronic RFRP-3 infusion also had higher basal circulating corticosterone levels. These results indicate a stimulatory action of RFRP-3 on the HPA axis, consistent with the dense expression of NPFF1R in the vicinity of CRH neurons. Importantly, co-infusion of RFRP-3 and GJ14 completely reversed the anxiogenic and HPA axis-stimulatory effects of RFRP-3. Here, we have established the role of RFRP-3 as a regulator of stress and anxiety. We also show that GJ14 can reverse the effects of RFRP-3 both in vitro and in vivo. Infusion of GJ14 causes anxiolysis, revealing a novel potential target for treating anxiety disorders.