Gonadotrophic Hormone Function in Persistent Estrous Rats with Hypothalamic Lesions.

Abstract

Hypothalamic regulation of gonadotropic hormone function was assessed in young adult female rats showing persistent vaginal estrus after placement of bilateral electrolytic lesions in pre-optic and anterior hypothalamic brain areas. Ovarian weight, normal up to 60 days post-operatively, eventually decreased (120-300 days). Significant hypertrophy of uterus and pituitary occurred. Compensatory enlargement of the remaining ovary in unilaterally oophorectomized rats was inhibited after destruction of the hypothalamus (25-60 days). Follicle stimulating hormone (FSH) was determined in sera and acid-saline pituitary extracts of operated rats by the human chorionic gonadotropin (HCG) augmentation method. FSH concentration in the pituitary was well maintained in lesioned, unilaterally castrate rats but serum titers were far below those in oophorectomized controls. The results indicate that the adenohypophysis in rats rendered persistent estrus by hypothalamic lesioning loses capacity to augment secretion of FSH under conditions of enhanced demand (unilateral oophorectomy).