Effects of testosterone propionate implants in the brain on the sexual behavior and peripheral tissue of the male rat

Abstract

The effects of testosterone propionate (TP) implanted in medial preoptic-anterior hypothalamic (MPO-AH) area, caudate-putamen, substantia nigra, and reticular formation on the sexual behavior were studied in castrated male rats. Either TP or cholesterol (C) was fused to the inside of 20-gauge cannula and bilaterally implanted in the brain of male rats not exhibiting ejaculatory patterns for 3 successive weeks after castration. Ejaculatory patterns were restored by TP implanted in all of the neural areas studied. No ejaculations were recorded in C-implanted animals. While the MPO-AH implanted animals tended to show ejaculatory patterns more frequently and in more tests than those having implants in other areas, the differences among groups were not statistically significant. Seminal vesicle weights and histological appearance of the seminal vesicles of TP-implanted animals were not reliably different from those implanted with C. Glans penis epithelium, however, was significantly more stimulated in the TP- than in C-implanted animals. Thus, evidence was obtained that androgen from the implants entered the general circulation and reached somatic organs and probably other neural areas. Using the hormone implantation technique, therefore, no reliable evidence was obtained to conclude that the MPO-AH is a special site for selectively utilizing androgen for controlling male sexual behavior.