Detailed distribution of neuropeptide FF receptors (NPFF1 and NPFF2) in the rat, mouse, octodon, rabbit, guinea pig, and marmoset monkey brains: A comparative autoradiographic study

The distribution of neuropeptide FF receptors (NPFF1 and NPFF2) was analyzed throughout the central nervous system of rodents (rat, mouse, Octodon degus, and guinea pig), rabbit, and marmoset monkey brains, representing three orders of mammals. Quantitative in vitro receptor autoradiography with [125I]EYF ([125I]EYWSLAAPQRF-NH2) and [125I]YVP ([125I]YVPNLPQRF-NH2) as specific radioligands for NPFF2 and NPFF1 receptors, respectively, was used. The NPFF2 receptor is predominantly expressed in all species, except in the central nervous system of Octodon degus, in which it is undetectable. The density of the NPFF1 subtype is low in rat and mice, moderate in octodon, rabbit, and monkey, and relatively high in the guinea pig. The present study reveals prominent species differences in the NPFF receptors expression in the brain. The distribution pattern of NPFF2 receptors in the diencephalon and the superficial layers of the spinal cord is consistent with a hypothesized potential role for NPFF in the modulation of sensory input and opioid analgesia. In contrast, the constant presence of NPFF1 receptors in the septum, the nucleus of the tractus solitarius, and the hypothalamus suggest its participation in neuroendocrine functions. Synapse 51:249–269, 2004. © 2003 Wiley-Liss, Inc.