Immunopresence and function of NGF/TrkA system in the uterus of rabbit (Oryctolagus cuniculus)

The aim of this study was to investigate the presence in rabbit uterus of the nerve growth factor (NGF) and its cognate receptor tyrosine kinase A (TrkA), as well as the in vitro effects of NGF on the production of prostaglandin E2 (PGE2) and PGF2α. A strong positivity for β-NGF was localized in the nucleus and cytoplasm of the uterine epithelial, glandular, stromal, miometrial, and endothelial cells, whereas the TrkA immunopresence was evidenced only in the cytoplasm of epithelial, glandular, and stromal cells. The Western blotting data confirm the specificity of the antisera used for the immunohistochemical detection of β-NGF and TrkA in the uterus. In uterine samples, a single band for each protein was found at approximately 55 kDa for β-NGF and 42 kDa for TrkA. β-NGF (30 nM minimum effective dose) increased the in vitro uterine release of PGF2α, whereas this neurotrophin did not affect that of PGE2. These results provide evidence that the NGF/TrkA system is present in the uterus of rabbits and that it affects the uterine synthesis of PGF2α. Since this uterine prostaglandin has a role in the modulation of the ovarian activity in mammals, these results shed a new light on the possible direct involvement of NGF/TrkA system in the physiological mechanisms regulating mammalian reproduction.