LUTEINIZATION OF OVARIAN GRAFTS IN RATS RELATED TO TREATMENT WITH TESTOSTERONE IN THE NEONATAL PERIOD
SUMMARY Male Wistar rats were castrated on the day of birth and divided into two groups; the first was injected with 0·1 mg. testosterone propionate (TP), on the day of castration and the second with 0·5 mg. TP after day 10. When 45 days old, all were grafted with an ovary in the kidney. Animals in the first group showed ovaries with ripening follicles without corpora lutea; those in the second group had corpora lutea at different stages of maturation. Ovaries grafted into female rats spayed on the day of birth developed luteinization even when injected with 0·5 mg. TP after the 10th day of life, but not if the hormone was injected earlier. Since the hypothalamus is sensitive to androgens only before the 10th day of life even in gonadectomized rats, it can be argued that the female pattern of gonadotrophin control does not correspond to the undifferentiated hypothalamus but depends on some active central mechanism. The period during which the hypothalamus is still sensitive to androgens would correspond to the undifferentiated equipotential stage.