Hypothalamic stimulation of follicle stimulating hormone (FSH) secretion from transplanted pituitaries following exposure to constant light.

Abstract

The effects of lesions in the basal median hypothalamus and of pinealectomy on the constant light-induced follicular development were evaluated in hypophysectomized rats with pituitary transplants. Adult hypophysec-tomized female rats received 2 pituitary homo-grafts 5–8 days post hypophysectomy. Lesions and pinealectomy along with their respective sham operations were performed 5–7 days after transplantation. Animals were exposed to constant light for 21 days. In some experiments animals received HCG for 3–4 days prior to termination of the experiments. FSH concentrations were evaluated by the Steelman-Pohley method. Constant light induced 22–55% increases in the ovarian weights and 36–50% increments in the uterine weights of hypophysectomized rats with pituitary transplants. No stimulation of uterine weights was obtained without HCG administration. Lesions in the basal median hypothalamus completely prevented the constant light-induced increases in both ovarian and uterine weights, indicating a signific...