RF-amide peptides
a family of peptides characterized by a common carboxy-terminal Arg-Phe-NH2 motif
play various physiological roles in the brain including the modulation of neuroendocrine signaling. Neuropeptide FF (NPFF) receptors exhibit a high affinity for all RF-amide peptides
which suggests that the neurons expressing these NPFF receptors may have multiple functions in the brain. However
the distribution of the neurons expressing NPFF receptors in the rat brain remains poorly understood. This study aimed to determine the detailed histological distribution of mRNA that encodes the neuropeptide FF receptors (Npffr1 and Npffr2) in the rat brain using in situ hybridization. Neurons with strong Npffr1 expression were observed in the lateral septal nucleus and several hypothalamic areas related to neuroendocrine functions
including the paraventricular nucleus (PVN) and arcuate nucleus
whereas Npffr2-expressing neurons were observed mainly in brain regions involved in somatosensory pathways
such as several subnuclei of the thalamus. Npffr1 expression was observed in 70% of corticotropin-releasing hormone neurons
but in only a small population of oxytocin and vasopressin neurons in the PVN. Npffr1 expression was also observed in the dopaminergic neurons in the periventricular nucleus and the dorsal arcuate nucleus
and in the kisspeptin neurons in the anteroventral periventricular nucleus. These results suggest that NPFFR1-mediated signaling may be involved in neuroendocrine functions
such as in reproduction and stress response. In conjunction with a detailed histological map of NPFFRs
this study provides useful data for future neuroendocrine research.
