Mechanisms triggering prostatic NE differentiation are poorly understood. Since dog and man naturally develop prostatic proliferative diseases with age, our objectives were to confirm the presence of NE cells in the dog prostate and test their hormonal regulation in both species.

Serotonin staining was examined by immunohistochemistry in 37 dog prostates: 17 from intact and 20 from castrated animals. In intact dogs, 9 prostates were normal and 8 hyperplastic. In the castrated group, 6 dogs were left untreated while androgens and estrogens were administered to 7 dogs, each. Human prostates were from 48 prostate cancer patients; half of them were submitted to androgen ablation prior to prostatectomy. The density of serotonin‐positive NE cells was expressed relatively to the number of acini.

Serotonin‐positive NE cells were morphologically similar in dog and human prostates and identified in all groups, independent of the hormonal status. NE cell densities were within the same range in normal and hyperplastic dog prostates but significantly higher after castration. Androgens and estrogens after castration restored NE cell density to normal values and induced luminal differentiation and basal metaplasia, respectively. In human, the density of serotonin‐positive NE cells was also significantly higher in benign glands after androgen ablation.

The dog is a suitable animal model and mimics the human, since androgen ablation favored prostatic NE differentiation in both species. The down‐regulation elicited by steroids suggests that the process may be reversible and hormonally‐repressed. Prostate 51: 117–125, 2002. © 2002 Wiley‐Liss, Inc.