Critical exposure time for androgenization by intracranial crystals of testosterone propionate in neonatal female rats.

The critical exposure time for neonatal treatment with testosterone propionate (TP) to induce anovulatory sterility was determined. Crystalline TP was applied to a groove on the external surface of 30 gauge hypodermic tubing. These tubes, either coated with TP or with cholesterol, were implanted bilaterally in the basal hypothalamus of the 3-day-old female rat and removed after 12, 24, 48, or 72 hr. At the time of implantation carbon markers were extruded from the same tubes to indicate in the adult the site of neonatal exposure to TP. Exposure of the basal hypothalamus to TP for 48 hr was necessary before more than 50% of the treated animals were rendered anovulatory by 100 days of age. When these same animals were laparotomized at 50 days of age only 43% were anovulatory even after a 72-hr exposure to TP. Ovarian compensatory hypertrophy was not affected by neonatal intracerebral TP implantation. Although implants of TP in the region of the hypothalamus including the ventromedial-arcuate area appeared t...