Effects of castration on the NGF and TrkA expression in the vas deferens and accessory male genital glands of the rat

Nerve Growth Factor (NGF) is a member of the neurotrophin family. Neurotrophins exert their effects by binding to corresponding receptors, which are formed by the tyrosine protein kinases TrkA, TrkB, and TrkC, and the low affinity p75NTR receptor. The role of neurotrophins in the biology of male genital organs is far from clear. In particular, little is known about the influence of sex hormones on the expression of neurotrophins and their receptors. In the present study, using immunohistochemistry and real time RT-PCR, we investigated the expression of NGF and TrkA in the vas deferens and accessory male genital glands in normal and castrated rats. In normal rats, both NGF- and TrkA-immunoreactivities were localized in the epithelial layer of the vas deferens and glands. NGF-immunoreactivity was also found in the musculature. The nerves were weakly immunoreactive in all the examined organs. After castration the immunoreactivies persisted. Real-time RTPCR experiments indicated that NGF and TrkA mRNA levels increased significantly in all the examined organs after castration. These results suggest that NGF and TrkA are expressed in the internal male genital organs of the rat and that their expression is downregulated by androgen hormones. We hypothesize NGF and TrkA play a role in the involutive processes which occur in these organs after castration.