Induction of Precocious Puberty in Newborn Female Guinea Pigs by a Positive Feedback Action of Estrogens

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Abstract
The existence of a positive feedback of estrogen on the gonadotropin-releasing mechanism at birth was tested in the female guinea pig. Estradiol benzoate (100 ng during the first 5 days of life) or HCG [human chorionic gonadotropin] (100 RU (rat units) during the first 5 days of life) induced a true precocious puberty, with similar characteristics to control animals (60% of animals ovulated at puberty age: corpora lutea present at the ovaries). The uterus was larger in ovulating than in nonovulating animals. Reserpine (2.5 mg/kg) on 15, 17 and 19 days of age did not modify the precocious puberty induced by estradiol at birth. Apparently exogenous or endogenous estrogen (induced by exogenous gondadotropin administration) have a positive feedback action on the newborn female guinea pig to release gonadotropin and develop puberty. These results are very differnt than those observed in the rat, and differences can be related to stage of somatic and nervous maturation atained by animals at birth.