Androgen sterilization produced by intracerebral implants of testosterone in neonatal female rats.

Abstract

To study the effects of intracerebral implantation of androgen in newborn female rats, 12 μg paraffin pellets, each containing 3 or 1 μg dissolved testosterone propionate (TP), were extruded bilaterally into the brains of 4-dayold female rats. Intact animals, rats receiving paraffin-TP pellets sc and rats with blank pellets devoid of TP in the brain served as controls. Rats treated with 10 μg TP in oil sc were included as reference groups. Hypothalamic paraffin-TP pellets at both dose levels significantly advanced vaginal opening. Moreover, 16/19 rats receiving 6 μg testosterone and 16/20 receiving 2 μg testosterone in the brain showed persistent vaginal estrus (PVE); 8/16 in the latter group showed PVE within 12 days after vaginal opening, whereas 8 developed PVE from 37 to 60 days after opening. These differences in delay in onset of PVE appeared to be related to site of placement of the pellets in the hypothalamus. Similar pellets placed sc abolished vaginal cyclicity in 7/15 rats (6 μg dose) and 4/1...