Distribution of fibroblast growth factor receptors and their co-localization with vasopressin in the choroid plexus epithelium.

Increasing evidence indicates that basic fibroblast growth factor (FGF2), a well-known mitogen, can regulate the synthesis and secretion of peptide hormones. FGF2 has also been recently shown to inhibit cerebrospinal fluid (CSF) formation and increase the number of dark choroid plexus epithelial cells. These latter FGF2 actions could be mediated by vasopressin (VP) synthesized by and released from choroidal epithelium. The present study was therefore designed to determine whether VP co-localizes with fibroblast growth factor receptors (FGFRs) in the choroid plexus epithelium. Using confocal laser-scanning microscopy, we demonstrated the apical (CSF-facing) distribution of FGFRs in epithelial cells. FGFRs were expressed on clusters of VP-positive cells, with the intensity of FGFR-immunopositive staining varying from one group of cells to the other. These observations are in line with the possible mediatory role of VP in the FGF2-dependent inhibition of CSF secretion and the induction of dark epithelial cells.