Expression of neurotrophin receptors in rat testis. Upregulation of TrkA mRNA with hCG treatment

We report the expression of TrkA, TrkB and TrkC mRNAs in adult rat testis. With in situ hybridisation a low signal for TrkB and TrkC could be seen in postmeiotic cells of the seminiferous epithelium, whereas no signal for Trk A could be observed in untreated animals. Animals treated with hCG showed a n induction of TrkA mRNA in premeiotic cells 12 h after the treatment, wher eas an injection with EDS had no effect on the expression of Trk mRNAs. Wit h the RNAse protection assay a low signal for TrkA was seen in whole testis of hCG treated animals. In staged tubules low expression was seen at stage s VII-XI of untreated animals. Animals injected with hCG revealed that TrkA induction was highest during stages VIIcd and VIII of the cycle. The disti nct expression pattern of these high-affinity neurotrophin receptors sugges ts different roles for neurotrophins during spermatogenesis. Induction of T rkA mRNA by hCG suggests that high-affinity binding of NGF during stages VI Icd-VIII in premeiotic cells is under control of the hypothalamic-pituitary -testicular axis. (C) 2001 Elsevier Science Ireland Ltd. All rights reserve d.