DIURNAL VARIATIONS OF PROLACTIN IN THE PLASMA OF MATURING FEMALE RATS BEARING HYPOTHALAMIC LESIONS

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Abstract
Previous evidence suggested a possible involvement of prolactin (PRL) in the induction of precocious puberty due to hypothalamic lesions in maturing female rats. In the present report the concentrations of PRL in plasma of lesioned and control rats were determined 3 times a day at 3 different periods of puberty. Lesions were produced in 20 day old rats by a radiofrequency current in the anterior hypothalamic area (AHA). Intact littermates were used as control. Respectively 23, 25 and 28 day old lesioned and control rats were bled at 0800, 1200 or 1600 h. PRL levels, measured by RIA [radioimmunoassay] were determined from plasma aliquots. In control rats, elevated plasma PRL levels were found in the afternoon. Hypothalamic lesion induced a tendency to elevate tonically the PRL plasma concentrations which was evident at 1600 h in 23 and 25 day-old rats and at 0800 and 1200 h in 28 day-old rats. PRL secretion is apparently modified by the effect of lesions in the AHA.