Anovulation in adult female rats after neonatal intracerebral implantation of oestrogen.

Four-day-old female rats were bilaterally implanted with paraffin micropellets containing 0.5% oestradiol benzoate (OB) into the mediobasal hypothalamus or the corticomedial amygdala. Controls received intracerebral paraffin pellets or two s.c. OB-paraffin implants. None of the treatments influenced the date of vaginal opening and vaginal cyclicity at 50 days of age. Permanent vaginal oestrus between 100 and 116 days of age and anovulatory ovaries at autopsy on day 116 were found in rats that had been implanted with OB into the mediobasal hypothalamus, but not in the remaining animals. The findings demonstrate that the delayed anovulatory syndrome can be induced in female rats by the neonatal intrahypothalamic implantation of a very low dose of OB, and that the corticomedial amygdala seems not to be a site of oestrogen action in this sterilizing effect.