Distribution and Characterization of Neuropeptide FF-like Immunoreactivity in the Rat Nervous System with a Monoclonal Antibody

Monoclonal antibodies against neuropeptide FF were produced and characterized. The antibodies are directed and highly specific to neuropeptide FF, and reactivity requires the C‐terminal dipeptide of neuropeptide FF (Arg‐Phe‐NH2). Tissue extracts from bovine spinal cord, rat spinal cord and hypothalamus were analysed by high‐pressure liquid chromatography coupled with radioimmunoassay using the characterized monoclonal antibody. Only one immunoreactive peptide was detected and it coeluted with authentic neuropeptide FF. Using this highly specific monoclonal antibody, the distribution of neuropeptide FF‐like immunoreactivity was further studied by indirect immunohistochemistry. Immunoreactivity was seen in two major cell groups in the rat brain. The largest cell group was located in the medial hypothalamus between the dorsomedial and ventromedial nuclei. The other one was found in the nucleus of the solitary tract. Fibres immunoreactive for neuropeptide FF were located in the lateral septal nucleus, amygdala, different hypothalamic areas, nucleus of the solitary tract, ventral medulla, trigeminal complex and the dorsal horn of the spinal cord. Spinal and sympathetic ganglia were non‐reactive. No neuropeptide FF immunoreactivity was seen in the gut autonomic nervous system or endocrine cells. The results show that neuropeptide FF‐like immunoreactivity has a clearly more limited distribution in the nervous system than typical brain–gut peptides.