Sexual Differences in the Hypothalamic Regulation of Prolactin Secretion12

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Abstract
Estrogen treatment of female rats ovariectomized when adult or of adult neonatally castrated males resulted, on the afternoon and evening of the 3rd day after initiation of treatment, in surges of prolactin secretion which reached 100 ng/ml. Males castrated when adult or androgen sterilized females ovariectomized when adult did not produce surges in response to estrogen treatment, prolactin levels remaining in the range of 10–20 ng/ml. In contrast to these sexual differences, baseline prolactin levels in untreated gonadectomized males or androgen sterilized females were significantly higher than in untreated gonadectomized females or neonatally castrated males. The surge of prolactin secretion in estrogen-treated female rats ovariectomized when adult was inhibited by a retrochiasmatic cut separating the anterior from the medial part of the hypothalamus. These results demonstrate fundamental sexual differences in the regulation of prolactin secretion. These differences may result from androgens inhibiting, in the neonatal animal, the organization of a rostral “surge center,” thus suppressing the potential to produce a surge of prolactin secretion. Androgens may also attenuate the functional capabilities of the medial hypothalamus to secrete prolactin inhibiting factor, resulting in higher tonic levels of prolactin. (Endocrinology90: 1154, 1972)

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