Distribution of novel RFamide-related peptide-like immunoreactivity in the mouse central nervous system

Recently, novel mammalian RFamide-related peptides (RFRPs) have been identified and suggested to increase prolactin release in the rodent. To assess possible functions of RFRPs, we investigated the distribution of RFRPs in the mouse central nervous system by immunochemical analyses. The quantitative analysis revealed that the concentration of RFRP-like substances was much higher in the brainstem and spinal cord than in other regions. Immunohistochemistry showed that RFRP-like immunoreactive perikarya were localized in the dorsomedial hypothalamic nucleus, the lateral superior olive, and the nucleus of the solitary tract. The dense networks of immunoreactive fibers were found in the lateral parabrachial nucleus, the lateral reticular nucleus, and the superficial layer of spinal trigeminal nucleus and dorsal horn of the spinal cord. Thus, RFRPs may participate not only in neuroendocrine functions but also in behavioral, sensory, and autonomic functions.