FAILURE OF LUTEOTROPHIC FUNCTION DUE TO PITUITARY GRAFTS IN RAT HYPOTHALAMUS

Neonatal pituitaries were grafted into the anterior hypothalamus of Wistar female rats. Controls received cerebral conical tissue or were sham operated. The effects of the grafts on subsequent estrous cycles were studied by daily vaginal smears, smears being continued in many cases after admission of fertile bucks and after spermatozoa appeared in the vaginal smears (indicating that copulation had occurred). Only 2 of 29 rats with neonatal pituitary tissue surviving in the anterior hypothalamus produced litters and 94 matings in these rats produced no litters. Ovulation and fertilization occurred normally, bur the copulatory induction of luteotrophic maintenance of the corpora lutea was absent. Pituitary grafted rats returned to estrus in a normal (unmated) cyclic manner after 57 fertile matings. This impairment of the luteotrophic response to copulation occurred with almost negligible frequency in cortex grafted or sham-operated controls and, if due to the grafted pituitary tissue, it must have been caused by prolactin from the graft, as prolactin cells alone were seen in all of the grafts. These findings confirm the possibility that prolactin may in some way auto-regulate its own secrction. © 1969 S. Karger AG, Basel.