IMMUNOHISTOCHEMICAL LOCALIZATION IN THE RAT-BRAIN OF AN EPITOPE CORRESPONDING TO THE FIBROBLAST GROWTH-FACTOR RECEPTOR-1

The localization of fibroblast growth factor receptor-1 was investigat ed in rat brain by immunohistochemistry using a polyclonal antibody ag ainst an acidic peptide sequence of chicken fibroblast growth factor r eceptor-1 For raising the antisera in rabbits, we synthesized the olig opeptide EDDDDEDDSSSEEKEAD which is a highly acidic region of chicken fibroblast growth factor receptor-1 The oligopeptide was used as a hap tenic antigen by conjugating with poly-L-glutamate as a carrier protei n. On immunospot assay, the best antiserum was capable of detecting 15 .7 pmols of both the chicken and its analogous human oligopeptides but failed to react even with up to 1 nmol of poly-L-glutamate, When rat brain homogenate was examined by Western blots, the antiserum revealed two bands with molecular weights of 145,000 and 75,000 corresponding to known sizes of the membrane-bound and secreted forms of the rat rec eptor, respectively. Immunohistochemistry in rat brain demonstrated th at putative fibroblast growth factor receptor-1 immunoreactivity sites were present mainly in neurons but also in tanycytes and ependymal ce lls. Positive neurons were distributed widely in various brain regions , but were particularly abundant in such regions as the lateral hypoth alamus, substantia nigra, locus coeruleus and raphe nuclei. The presen t study suggests that fibroblast growth factor receptor-1 is expressed preferentially in certain neuronal systems that appear to be under th e influence of fibroblast growth factors in the normal brain. The resu lt should facilitate study of the functional significance of fibroblas t growth factors in these brain neurons.