Ovulatory Response to Gonadotropin Administration in Maturing Rats with Lesions in the Anterior Hypothalamic Area

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Abstract
The ovulatory response to PMS [pregnant mare''s serum gonadotrophin] HCG [human chorionic gonadotropin] and estradiol valerate (E2V) was studied at different ages in maturing rats lesioned in the anterior hypothalamic area (AHA). At 20 days of age, rats were lesioned by high frequency current in the AHA, while intact littermates were used as controls. AHA lesions result in advancement of puberty as previously reported. After (16 h) a single s.c. injection of 10 IU of HCG, 86% of the lesioned and none (0%) of the control animals ovulated at 25 days of age. At the same time, 72 h after a single injection of 10 IU of PMS, control animals did not ovulate, while 7% of the lesioned animals did. The ovulatory response was similar between lesioned and intact rats when challenged with 30 IU of PMS or with combinations of PMS + HCG. Only lesioned animals (33%) ovulate at 25 days of age, 66 h after a single dose of estradiol (0.05 .mu.g/rat). AHA lesions that induced precocious puberty are probably associated with an increase in ovarian sensitivity to gonadotropins.