Effects of castration on the expression of TrkB and p75NTR in the vas deferens and male accessory genital glands of the rat.

Brain-derived neurotrophic factor (BDNF) is a growth factor belonging to the family of neurotrophins. Neurotrophins exert their effects by binding to corresponding receptors, which are formed by the tyrosine receptor 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 neurotrophin receptors. In the present study, using immunohistochemistry, we investigated the distribution of TrkB and p75NTR in the vas deferens and accessory male genital glands in normal and castrated rats. In normal rats, both TrkB and p75NTR immunoreactivities were localized in the epithelial layer of the vas deferens and prostate gland. The nerves were immunoreactive in all the examined organs. Castration induced the loss of both TrkB and p75NTR immunoreactivities in the epithelial layer. On the contrary, both receptors persisted or, as in the case of p75NTR, increased in the nerves after castration. These results show that receptors that bind BDNF are expressed in the internal male genital organs of the rat and that their expression is differently regulated by androgen hormones. It can be hypothesized that BDNF, via interacting with p75NTR, has a role in the castration-induced regression of the sympathetic nerves