PROTEIN GENE-PRODUCT-9.5 IN THE DEVELOPING AND MATURE RAT VOMERONASALORGAN

Protein gene product 9.5 (PGP 9.5) was immunocytochemically identified in structures of the developing and mature rat vomeronasal organ (VNO ). This study started with embryos at 17 days of gestation. By this st age, PGP 9.5 was immunolocalized within bath the receptor cells of the neuroepithelium and cells of the receptor-free epithelium, located on the opposite side of the lumenal space. Nerve fibers surrounding the nascent vomeronasal vein also showed PGP 9.5 immunoreactivity. Labelin g was retained in the neuroepithelium and nerve fibers around the vein during development and into adulthood. Within the pool of receptor ce lls of the adult neuroepithelium, labeling was observed within the cyt oplasm of the somata and dendrites; some receptor cells also expressed nuclear labeling. The number of immunoreactive cells in the receptor- free epithelium appeared to increase postnatally but by adulthood immu noreactivity virtually was absent. These results suggest a role for PG P 9.5 in development and maturation of the VNO and a continuing role w ithin the steadily renewing receptor cell population found in the matu re neuroepithelium. The findings of this study also suggest that PGP 9 .5 is localized within the nerve fibers surrounding the vomeronasal ve in from early in development through adulthood.