Modulatory Effect of Testosterone on the Serotoninergic Control of Prolactin Secretion in Prepubertal Rats

The administration of 5-hydroxytryptophan (5-HTP) induced a prolactin release in male and female prepubertal rats at 20 days of age. This response was significantly higher in male than in female rats. Neonatal androgenization of the females significantly increased the release of prolactin induced by 5-HTP treatment compared to the values observed in males; thus, the neonatal exposure to androgens seems to be responsible for the sexual differences in the prolactin response to 5-HTP. In a second series of experiments the effect of this serotoninergic precursor on prolactin release in prepubertal (16, 26, and 30 days of age), peripubertal (45-day-old) and adult male rats was studied. Castration significantly decreased the prolactin release response to 5-HTP in prepubertal rats. The administration of testosterone to castrated rats markedly increased the prolactin release response to 5-HTP. Neither castration nor testosterone administration modified the prolactin response to 5-HTP in peripubertal and adult rats. These results appear to indicate that testosterone modulates the serotoninergic control of prolactin secretion during the prepubertal stage. The control of prolactin levels could be one of the mechanisms by which testosterone participates in the sexual maturation.